Question 1. Difference between active and passive immunity.
Answer:

“Understanding immunity through FAQs: Q&A explained”

“Importance of studying immunity for BSc Nursing students: Questions explained”

Question 2. Write a short note on Immunoglobulin (Ig)
Answer:

Immunoglobulin Definition: Immunoglobulins are glycoprotein molecules that are produced by plasma cells in response to an immunogen and which function as antibodies. The immunoglobulins derive their name from the finding that they migrate with globular proteins when antibody-containing serum is placed in an electrical field.

Immunoglobulin classes: The immunoglobulins can be divided into five different classes, based on differences in the amino acid sequences in the constant region of the heavy chains. All immunoglobulins within a given class will have very similar heavy chain constant regions. These differences can be detected by sequence studies or more commonly by serological means (i.e. by the use of antibodies directed to these differences).

IgG – Gamma heavy chains

IgM – Mu heavy chains

IgA – Alpha heavy chains

IgD – Delta heavy chains

IgE – Epsilon heavy chains.

“Common challenges in understanding immunity effectively: FAQs provided”

Question 3. WIDAL Test.
Answer:

Introduction Of Widal Test: In 1896 and named after its inventor, Georges-Fernand Widal, is an indirect agglutination test for enteric fever or undulant fever whereby bacteria causing typhoid fever is mixed with a serum containing specific antibodies obtained from an infected individual.

• In cases of Salmonella infection, it is a demonstration of the presence of O-soma false positive result. Test results need to be interpreted carefully to account for any history of enteric fever, typhoid vaccination, and the general level of antibodies in the populations in endemic areas of the world.
• Widal test is a serological test that is done for the diagnosis of typhoid fever caused by the Salmonella organism. This test detects the “O” and “H” antigens of Salmonella typhi and paratyphi A, B, and C. When facilities for culturing are not available, the Widal test is reliable and can be of value in the diagnosis of typhoid fevers in endemic areas.

WIDAL Test Clinical significance: Typhoid fever or enteric fever occurs when S. Typhi, S. Paratyphi A, S. Paratyphi B, and S. Paratyphi C infect the human body. The body responds to this antigenic stimulus by producing antibodies whose titer rise slowly in the early stages, to a maximum, and then slowly falls till it is undetectable.

Persons with typhoid fever carry the bacteria in their bloodstream and intestinal tract. Transmitted through the ingestion of food or drink contaminated by the feces or urine of infected people

“Steps to explain types of immunity: Innate vs adaptive: Q&A guide”

Question 4. ELISA Test.
Answer:

Enzyme-linked Immunosorbent Assay (ELISA): Enzyme-linked immunosorbent assay, commonly known as ELISA or EIA), is similar in principle to RIA but the radioactive tag used in RIA techniques can be replaced with an enzyme. When this enzyme is linked to an antibody and used to detect and measure other antibodies or antigens, the assay is called the enzyme-linked immunosorbent assay (ELISA).

An enzyme conjugated with an antibody reacts with a colorless substrate to generate a colored reaction product. Such a substrate is called a chromogenic substrate. Enzyme-linked immune sorbent assay is a highly sensitive, highly specific, and less expensive technique used in serology to detect antigens or antibodies.

Types of ELISA

1. Indirect ELISA
2. Sandwich ELISA
   • Single antibody or direct sandwich ELISA
   • Double-antibody or indirect sandwich ELISA
3. Competitive ELISA

Uses Of Elisa: ELISA is a simple and versatile technique. It needs only microliter quantities of reactants. ELISA has been used to detect antigens and antibodies of various microorganisms.

Elisa Examples

1. Parasites
   • Entamoeba histolytica antigens in feces
   • Toxoplasma antigens in the patient’s serum.
2. Bacteria
   • Haemophilus influenza antigens in spinal fluid
   • β-hemolytic streptococcal antigen in spinal fluid
   • Labile enterotoxin of E. coli in stools.
   • To detect antibody specific for:
3. Mycoplasmas
   • Chlamydiae
   • Borrelia burgdorferi.
4. Viruses
   • To detect antibody specific for:
   • Hepatitis virus antigens
   • Herpes simplex viruses 1 and 2
   • Respiratory syncytial virus (RSV)
   • Cytomegalovirus

Read And Learn More: Bsc Nursing 1st Year Microbiology Previous year Question and Answers

• • Human immunodeficiency virus (HIV)
  • Rubella virus (both IgG and IgM)
  • Adenovirus antigens—in nasopharyngeal specimens.

“Role of antibodies in immune response: Questions answered”

Question 5. Difference between Immediate and Delayed Hypersensitivity.
Answer:

“How do immune cells fight infections? FAQ explained”

Question 6. Classify immunoglobulin and write in short about IgG.
Answer:

Immunoglobulin classes: Human serum contains five classes of immunoglobulins—IgG, IgA, IgM, IgD, and IgE in the descending order of the concentration.

Immunoglobulin G (IgG)

1. This is the major immunoglobulin in human serum, accounting for about 80 percent of the total immunoglobulin pool.
2. It has a sedimentation coefficient of 7S and a molecular weight of 150,000.
3. It contains less carbohydrates than other immunoglobulins.
4. The normal serum concentration of IgG is about 8 to 16 mg per ml.
5. It has a half-life of 23 days—the longest of all of the immunoglobulin isotypes.
6. IgG is the predominant immunoglobulin in blood, lymph, peritoneal fluid, and cerebrospinal fluid, and it is distributed nearly equally between extra and intravascular spaces. Therefore, IgG is particularly suitable for passive immunization done by the transfer of serum-containing antibodies (antiserum).
7. Four subclasses of IgG (Ig1, Ig2, Ig3, Ig4) have been recognized. Each subclass possesses a distinct type of γ chain which can be identified with specific antiserum. They constitute about 65 percent, 23 percent, 8 percent, and 4 percent respectively of the total human IgG.
8. Catabolism of IgG is unique in that it varies with its serum concentration. When its level is raised, as in chronic malaria, kala-azar, or myeloma, the IgG synthesized against a particular antigen will be catabolized rapidly and may result in a particular antibody deficiency. Conversely, in hypogammaglobulinemia, the IgG given for treatment will be catabolized only slowly.

Functions of IgG: IgG is a very versatile molecule. It may be considered a general-purpose antibody, protective against those infectious agents which are active in the blood and tissues. It is protective against those microorganisms that are active in blood or tissue.

“Early warning signs of gaps in understanding immunity basics: Common questions”

Question 7. Types of Vaccines.
Answer:

A vaccine [Latin vacca, cow] is a preparation from an infectious agent that is administered to humans and other animals to induce protective immunity against a given disease.

Types of Vaccines

1. Live Vaccines: Live vaccines (for example, BCG, measles, oral polio) are prepared from live (generally attenuated) organisms. These organisms have been passed repeatedly in the laboratory in tissue culture or chick embryos and have lost their capacity to induce full-blown disease but retain their immunogenicity. In general, live vaccines are more potent immunizing agents than killed vaccines.
2. Killed (Inactivated) Vaccines: Organisms killed by heat or chemicals, when infected into the body stimulate active immunity. They are usually safe but generally less efficacious than live vaccines.
3. Toxoids: Certain organisms produce exotoxins, for example, diphtheria, and tetanus bacilli. The toxins produced by these organisms are detoxicated and used in the preparation of vaccines.
4. Cellular Fractions: Vaccines, in certain instances, are prepared from extracted cellular fractions, for example, the meningococcal vaccine from the polysaccharide antigen of the cell wall, the pneumococcal vaccine from the polysaccharide contained in the capsule of the organism and hepatitis B polypeptide vaccines. Although the duration of experience with these vaccines is limited, their efficacy and safety appear to be high.
5. Mixed or Combined Vaccine: If more than one kind of immunizing agent is included in the vaccine, it is called a mixed or combined vaccine. The following are some of the well-known combinations
   1. DPT (Diphtheria-pertussis-tetanus)
   2. DT (Diphtheria-tetanus)
   3. DP (Diphtheria-pertussis)
   4. DPT and typhoid vaccine
   5. MMR (Measles, mumps and rubella)
   6. DPTP (DPT plus inactivated polio).
6. DNA Vaccines: A DNA vaccine elicits protective immunity against a microbial pathogen by activating both branches of the immune system: humoral and cellular. Long-lasting memory are cells also are generated.
   • DNA Vaccines Examples: At present, there are human trials underway with several different DNA vaccines against malaria, AIDS, influenza, hepatitis B, and herpes virus.

“Asymptomatic vs symptomatic effects of ignoring immunity principles: Q&A”

Question 8. Explain National immunization scheduled.
Answer:

National Immunization Schedule: The first visit may be made when the infant is 6 weeks old the second and third visits, at intervals of 1 to 2 months. Oral polio vaccine may be given concurrently with DPT. BCG can be given with any of the three doses but the site for the injection should be different. The schedule also covers immunization of women during pregnancy against tetanus. National immunization scheduled.

“Can targeted interventions improve outcomes using immunity knowledge? FAQs provided”

Question 9. Agglutination.
Answer:

Agglutination: It is an antigen-antibody reaction, in which a particulate antigen combines with its antibody in the presence of electrolytes at an optimal temperature and pH, resulting in visible clumping of particles. It differs from precipitation in which soluble antigen is present in contrast to particulate antigen of agglutination. Principles governing agglutination are the same as that of precipitation.

Agglutination occurs when antigen and antibody are present in optimal proportions. Lattice formation hypothesis holds good for agglutination too. The zone phenomenon may occur when either an antigen or an antibody is in excess.

Types of Agglutination Reaction

1. Slide Agglutination: Test A uniform suspension of antigen is made in a drop of saline on a slide or tile and a drop of the appropriate antiserum is added. Clumping occurs instantly or within seconds when the agglutination test is positive.
   • Slide Agglutination Uses:
     • It is a routine procedure to identify the bacterial trains isolated from clinical specimens. One example is to identify Salmonella species.
     • It is also used for blood group and cross-matching.
2. Tube Agglutination Test: This is a standard quantitative method for determination of antibodies. Serum is diluted serially by doubling dilution in test tubes. An equal volume of a particulate antigen is added to all tubes. The highest dilution of the scrum at which agglutination occurs is antibody titer. Tube agglutination is routinely employed for antibody detection in the diagnosis of Lyphoid (Widal test). brucellosis and typhus fevers (Weil-Felix reaction).

“Differential applications of active vs passive immunity: Questions answered”

Question 10.Immunoprophylaxis.
Answer:

Medical definition of immunoprophylaxis: the prevention of disease by the production of active or passive immunity. Immunoprophylaxis Protection against infectious diseases by (immunization) acquired by the individual either passively or actively:

1. Passive acquired immunity
2. 2- Active acquired immunity

1. Passive acquired immunity
   • Ready-made Ab transferred to individual giving rapid protection and short-lasting immunity: a-Naturally acquired passive immunity Occurs when antibodies are transferred from mother to fetus (IgG ) or in colostrum (Ig A).
   • b- Artificially acquired passive immunity Short-term immunization by injection of
     antibodies, For example: injection of antitoxic serum for treatment of diphtheria or tetanus. – injection of gamma globulin that are not produced by recipient’s cells, to hypogammaglobulin children.
2. Active acquired immunity:
   • An individual actively produces his own Ab. Immunity develops slowly and long-lasting due to the development of immunological memory
   • a-Natural active acquired immunity The person becomes immune as a result of previous exposure to a live pathogen
   • b-Artificially active acquired immunity A vaccine stimulates a primary response against the antigen without causing symptoms of the disease.

“Difference between innate and adaptive immunity: Q&A explained”

Question 11. Difference between oral (OPV) and killed (IPV) Polio vaccine.
Answer:

Question 12. Difference between IgG and IgM.
Answer:

“Most common complications of poorly understood immunity concepts: FAQs”

Question 13. Define immunity.
Answer:

Immunity Definition: Immunity Latin immunis, free of burden] refers to the resistance exhibited by the host towards injury caused by microorganisms and their products. Immunity is the capacity of multicellular organisms to resist harmful microorganisms.

Question 14. Classify the immunity types.
Answer:

Immunity Classification: Immunity against infectious diseases is of different types. The discrimination between self and nonself, and the subsequent destruction and removal of foreign material, is accomplished by two arms of the immune system, the innate (or “natural”) immune system, and the adaptive (or “acquired”), specific immune system.

Immunity

1. Innate (or natural) immunity
   1. Nonspecific
      • Species
      • Racial
      • Individual
   2. Specific
      • Species
      • Racial
      • Individual
2. Acquired (or adaptive) immunity
   1. Active
      • Natural
      • Artificial
   2. Passive
      • Natural
      • Artificial

“Why are immunity mechanisms often misunderstood in practice? Questions answered”

Question 15. Explain the mechanism of innate immunity.
Answer:

Mechanisms of Innate Immunity

1. Epithelial Surfaces
   1. Skin: It not only acts as a mechanical barrier to microorganisms but also provides bactericidal secretions. The high concentration of salt in drying sweat, the sebaceous secretions, and long-chain fatty acids contribute to bactericidal activity.
   2. Respiratory tract: The inhaled particles are arrested in the nasal passages on the moist mucous membrane surfaces. The mucous secretions of the respiratory tract act as a trapping mechanism and hair-like cilia propel the particles toward the pharynx where it is swallowed or coughed out. The cough reflex acts as an important defense mechanism,
   3. Intestinal tract: The mouth possesses saliva which has an inhibitory effect on many micro-organisms. Some bacteria may be swallowed and are destroyed by the acidic pH of gastric juices.
   4. Conjunctiva: Tears have a major role in flushing away bacteria and other dust particles. In addition, lysozyme present in tears has a bactericidal action.
   5. The Genitourinary tract: The flushing action of urine eliminates bacteria from the urethra . The acidic pH of vaginal secretions in females, due to the fermentation of glycogen by lactobacillus (normal flora), renders the vagina free of many pathogens.
2. Antibacterial Substances: Besides specific antibody formation, there are number of nonspecific antibacterial substances present in blood and tissues. These substances are properdin, complement, lysozyme, etc.
3. Cellular Factors: Once the infective agent has crossed the barrier of epithelial surfaces, the tissue factors come into play for defense.)

“Cost of ignoring immunity principles vs benefits of systematic approaches: Q&A”

Question 16. Write a short note on IgM.
Answer:

Immunoglobulin M (IgM)

1. About 10 percent of normal serum Igs consists of this class.
2. It is a heavy molecule (19S; MW 900,000 to 1,000,000 daltons, hence called a ‘millionaire molecule’).
3. The normal serum level of IgM is 1.2 mg/ml.
4. It has a half-life of about 5 days.
5. IgM is the first immunoglobulin to appear after exposure to an antigen.
6. In the circulation, IgM exists as a pentamer of five four-chain units. The five identical IgM monomers are connected to each other by a polypeptide joining the J chain. Polymerization of the subunits depends upon the presence of the J chain as with IgA. Monomeric IgM and IgD are present on the surface of mature, naive B cells.
7. IgM contains 10 Fab fragments, and thus 10 antigen binding sites. Though the theoretical valency is ten, this is observed only with small haptens. The effective valency falls to five with larger antigens, probably due to steric hindrance. Most of IgM (80 percent) is intravascular in distribution.
8. Phylogenetically IgM is the oldest Ig class. IgM is the first class of antibody produced during the primary immune response. It is also the earliest to be synthesized by a fetus beginning by about 20 weeks of age. As it cannot cross the placental barrier, the presence of IgM in the fetus or newborn indicates intrauterine infection. Its detection is, therefore, useful for the diagnosis of congenital infections such as syphilis, rubella, human immunodeficiency virus (HIV) infection, and toxoplasmosis.
9. They are relatively short-lived hence their demonstration in the serum indicates recent infection.
10. Treatment of serum with 0.12 M 2-mercaptoethanol selectively destroys IgM without affecting IgG antibodies. This provides a simple method for differential estimation of IgG and IgM antibodies.
11. Isohemagglutinins (anti-A and anti-B) and antibodies to S. Typhi O antigen and Wassermann reaction antibodies in syphilis are usually IgM.
12. IgM agglutinates bacteria, activates complement by the classical pathway, and enhances the ingestion of pathogens by phagocytic cells. IgM is normally restricted to the intravascular space because of its high molecular weight.

The post BSc Nursing 1st Year Microbiology Nursing Chapter 5 Immunity Question And Answers appeared first on BDS Notes.

Question 1. Pathogenicity of staphylococcus aureus.
Answer:

Pathogenesis Staph. aureus is an important pyogenic organism and lesions are localised in nature in contrast to streptococcal lesions which are spread in nature

Thick creamy pus is formed in staphylococcal infections Staphylococcal diseases may be classified as:

Cutaneous and deep infections; food poisoning, nosocomial infections, skin exfoliative diseases and toxic shock syndrome.

1. Cutaneous Infections: Superficial infections include pustules, boils, carbuncles, abscesses, styes, impetigo, pemphigus neonatorum, and wound and burn infections.
2. Deep Infections: These include osteomyelitis, tonsillitis, pharyngitis, sinusitis, pneumonitis, empyema, endocarditis, meningitis, bacteriaemia septicemia, and pyemia.
3. Food Poisoning: Staphylococcal food poisoning may follow 2-6 hours after the ingestion of contaminated food which contains preformed enterotoxin of Stap. aureus.
4. Nosocomial Infections: They are an important cause of hospital-acquired infections.
5. Skin Exfoliative Diseases: These diseases are produced by the strains of Staph. aureus that produce exfoliative toxin. Stripping of the superficial layers of the skin from the underlying tissue occurs in the various exfoliative syndromes caused by staphylococci (bullous impetigo, pemphigus neonatorum, Ritter’s disease). Staphylococcal scalded skin syndrome (SSSS) is one example of an exfoliative disease in which toxin spreads systemically.
6. Toxic Shock Syndrome (TSS): It is caused by toxin shock syndrome toxin (TSST-1). Although TSS became widely known in association with the use of tampons by menstruating women, it occurs in other situations also.

“Understanding pathogenic organisms through FAQs: Q&A explained”

Question 2. Pathogenicity of Streptococcus pyogenes.
Answer:

Pathogenesis: Str. Pyogenes produces pyogenic infections with a tendency to spread locally. Nonsuppurative sequelae of, local infections include acute glomerulonephritis are rheumatic fever

1. Pyogenic Infections

Respiratory infections: Sore throat (acute tonsillitis and/ or pharyngitis) is the most common of streptococcal diseases. Scarlet fever It consists of a combination of sore throat and generalised erythematous rash. It is caused by a strain producing the erythrogenic toxin.

Skin infections: Str. Pyogenes causes suppurative infections of the skin with a predilection to produce lymphangitis and cellulitis. The two typical streptococcal skin infections are erysipelas and impetigo. These skin infections are the main cause leading to acute glomerulonephritis children in the tropics.

Other pyogenic infections

1. Puerperal sepsis: Str pyogenes was an important cause of puerperal sepsis, It used to take a heavy toll of life before antibiotics became available.
2. Sepsis: Infections of skin lesions (eczema, psoriasis, scabies), wounds and burns. Pyaemia, septicemia, abscess in internal organs (brain, lung, liver, and kidney).

2. Non-Suppurative Complications: Str. Pyogenes infections are sometimes followed by two important non-suppurative sequelae, acute rheumatic fever and acute glomerulonephritis. These complications occur one to four weeks after the acute infection. Str. pyogenes is no longer detectable when these complications set in.

• The latent period suggests an immune response. Rheumatic fever is often preceded by sore throat while acute glomerulonephritis by the skin infection.
• These sequelae or complications are believed to be the result of hypersensitivity to some streptococcal components. Rheumatic fever may follow infection with any serotype of Str. pyogenes while acute glomerulonephritis is caused by only few nephritoginic type.

“How do pathogenic organisms cause diseases? FAQ answered”

Question 3. Difference between exotoxins and endotoxins.
Answer:

Exotoxins

1. They are lipopolysaccharides in nature.
2. They are heat labile
3. They are actively secreted by living cells into medium.
4. Highly antigenic stimulates the formation of antitoxin that neutralizes.
5. They are converted into toxoid by formaldehyde.
6. Enzymic in action.
7. They have specific pharmacological effect to each toxin.
8. They have very high potency.
9. They are highly specific for particular tissue example, tetanus toxin for the central nervous system.
10. They do not produce fever in host.
11. They are mainly produced by Gram-positive bacteria and also by some Gram-negative bacteria.

Endotoxins

1. They are protein (polypeptide) and molecular weight 10,000 to 900,00.
2. Heat stable
3. Form integral part of the cell wall and released on disruption of the bacterial cell.
4. Weakly antigenic: antitoxin is not formed but antibodies against polysaccharides are raised.
5. They can not be toxoided.
6. No enzymic in action.
7. Nonspecific action of all endotoxins.
8. They have low potency
9. They are nonspecific in action
10. They produce fever in host
11. They are produced by Gram-negative bacteria.

“Importance of studying pathogenic organisms for BSc Nursing students: Questions explained”

Question 4. Pathogenicity of pneumococcus pneumonia.
Answer:

Pneumococci colonize the human nasopharynx and may cause infection of the middle ear, paranasal sinuses, and respiratory tract by direct spread.

Pneumonia: Pneumococci are one of the most common bacteria causing pneumonia, both lobar and bronchopneumonia. They also cause acute tracheobronchitis and empyema. Bacteremia may complicate pneumococcal pneumonia. This can result in metastatic involvement of the meninges, joints, and, rarely, the endocardium.

Lobar Pneumonia: In adults, types 1-8 are responsible for about 75 percent of cases of pneumococcal pneumonia. In children, types 6, 14, 19, and 23 are frequent causes. Pneumonia results from aspiration of pneumococci contained in upper airway secretions into the lower respiratory tract.

• When the normal defences are compromised by viral infection, anesthesia, chilling or other factors, pneumococci multiply, penetrate the bronchial mucosa, and spread through the lung along peribronchial tissues and lymphatics.
• Contiguous spread commonly results in inflammatory involvement of the pleura. This may progress to empyema. Pericarditis is another uncommon but well recognized complication.

Bronchopneumonia: Bronchopneumonia is almost always a secondary infection. This may be caused by any serotype of pneumococcus. Other causative agents responsible for bronchopneumonia include Staph. aureus, K. pneumoniae, Str. pyogenes, H. influenzae, Fusobacterium species, and Bacteroides. Bronchopneumonia is frequently a terminal event in aged and debilitated patients

Question 5. Difference between primary and secondary tuberculosis.
Answer:

Difference between primary and secondary tuberculosis.

“Common challenges in understanding pathogenic organisms effectively: FAQs provided”

Question 6. Laboratory diagnosis for mycobacterium tuberculosis.
Answer:

Laboratory Diagnosis: Bacteriological diagnosis can be established by microscopy, culture examination, or by animal inoculation test. established by

1. Specimen: Specimen collection depends on the site of involvement. Tuberculosis may involve lungs (pulmonary) or sites other than lungs (extrapulmonary).

1. Pulmonary tuberculosis: Sputum is the most common specimen. It is collected in a clean wide-mouthed container. A morning specimen may be collected on three consecutive days. If sputum is scanty, a 24-hour specimen may be collected. When sputum is not available, laryngeal swab or bronchial washings are collected. In children, gastric washings may be examined as they tend to swallow sputum.
2. Meningitis: Cerebrospinal fluid (CSF) from tuberculous meningus (TBM) often forms a spider web clot on standing examination of which may be more useful than of fluid.
3. Renal tuberculosis: Three consecutive days morning samples of urine are examined.
4. Bone and joints tuberculosis: Aspírated fluid
5. Tissue: Blopsy of tissue.

2. Direct Microscopy: Smear is made from the specimen and stained by the Ziehl-Neelsen technique It is examined under oil immersion lens.

• The acid-fast bacilli (AFB) are bright red bacilli against a blue background. appear as A negative report should not be given till at least 300 fields have been examined.
• Grading of smears is done according to number of bacilli seen. If a large number smears are to be examined, fluorescent microscopy is more convenient.
• Smears are stained with fluorescent dyes such as auramine ‘O’ or auramine rhodamine and examined under ultraviolet light. The bacilli appear as bright bacilli against a dark background.

3. Concentration of Specimens Concentration of a specimen is done to achieve:

• Homogenization of the specimen
• Decontamination i.e. To kill other bacteria present in the specimen.

Read And Learn More: Bsc Nursing 1st Year Microbiology Previous year Question and Answers

• Concentration i.e. To concentrate the bacilli in a small volume without inactivation.
• Such concentrate is used for culture and animal inoculation tests besides smear preparation. Several concentration methods are in use.

4. Serology Serology includes the detection of anti-mycobacterial antibodies in patient serum. Various methods such as enzyme-linked immunosorbent assay (ELISA), radioimmunoassay (RIA), and latex agglutination assay have been employed. The diagnostic utility of these antibodies is equivocal. WHO has banned the use of these tests for the diagnosis of active tuberculosis.

5. Molecular Methods Polymerase chain reaction (PCR) is a rapid method in the diagnosis of tuberculosis. It is based on DNA amplification and has been used to detect M. tuberculosis directly in clinical specimens.

Question 7. Pathogenesis of Tuberculosis.
Answer:

Pathogenesis of Tuberculosis: The source of infection is usually an open case of pulmonary tuberculosis. The mode of infection is by direct inhalation of aerosolized bacilli contained in droplet nuclei of expectorated sputum tubercle bacilli are acquired from persons with active disease who are excreting viable bacilli by means of coughing, sneezing, or talking.

• Airborne droplet nuclei containing bacteria, 1 to 5 µm, enter the respiratory tract of an exposed individual and are deposited in the lung alveoli.
• Infection also occurs infrequently by ingestion, for example, through infected milk, and rarely by inoculation.
• The initial infection with M. tuberculosis is referred to as a primary infection. Subsequent disease in a previously sensitized person, either from an exogenous source or by reactivation of a primary infection, is known as postprimary (secondary or reinfection) tuberculosis with quite different pathological features.

“Why is early learning of pathogens critical for nursing success? Answered”

Question 8. Difference between lepromatous and tuberculoid leprosy.
Answer:

Question 9. Pathogenesis of Salmonella Typhi. or enteric fever.
Answer:

Pathogenesis: S. typhi, S. paratyphi A, and usually S. paratyphi B are confined to human beings. The majority of other salmonellae are primarily infective for animals and human beings are secondarily infected.

Salmonellae causes three types of clinical syndrome in human beings, enteric fever, septicaemia, and gastroenteritis.

Enteric Fever: The term enteric fever includes typhoid fever (S. typhi) and paratyphoid fever (S. paratyphoid A, B, C). Infections due to S. typhi and S. paratyphi A are prevalent in India.

Typhoid fever: The infection is acquired by ingestion through contaminated food and water. The incubation period is usually 7-14 days.

The clinical course may vary from mild pyrexia to a fatal Culminating disease. The characteristic features are hepatosplenomegaly, stepladder pyrexia with relative bradycardia, and leucopaenia. Skin rashes known as rose spots may appear during the second or third week.

Paratyphoid fever: Paratyphoid fever resembles typhoid fever but is milder, S. paratyphi A, B, and C cause paratyphoid fever.

“Steps to explain types of pathogenic organisms: Bacteria vs fungi: Q&A guide”

Question 10. Laboratory diagnosis of Enteric Fever.
Answer:

Laboratory Diagnosis: Bacteriological diagnosis of enteric fever consists of

1. Isolation of bacilli.
2. Demonstration of antibodies.

1. Isolation of Bacilli: This may be done by culture of specimens like blood, feces, urine, aspirated duodenal fluid, etc. The selection of relevant specimens depends upon duration of the illness which is very important for the laboratory diagnosis of enteric fever

2. Demonstration of Antibodies.

Widal Test: It is an agglutination test for the detection of agglutinins (H and 0) in patients with enteric fever. Salmonella antibodies start appearing in the serum at the end of first week and rise sharply during the third week of enteric fever. Two specimens of sera at an interval of 7 to 10 days are preferred to demonstrate a rising antibody titre.

Question 11. Shigella dysentriae.
Answer:

Shigellae cause bacillary dysentery. Humans are the only known reservoir of Shigella organisms infection occurs by ingestion. The infection is highly communicable because of the low infective dose required to produce the disease.

The minimum infective dose is low, as few as 10-100 bacilli being capable of initiating the disease, probably because they survive gastric acidity better than other enterobacteria.

• Shigella spp. are pathogens of man and other primates, and the pathogenesis of infection with these bacteria and entero-invasive E. coli (EIEC) is very similar.
• Shigella cause disease by invading and replicating in cells lining the colonic mucosa. After reaching the large intestine, the shigellae multiply in the gut lumen.
• The shigellae multiply within the epithelial cells and spread laterally into adjacent cells, where cell-to-cell passage occurs, and deep into the lamina propria. The infected epithelial cells are killed and the lamina propria and submucosa develop an inflammatory reaction with capillary thrombosis.
• Bacillary dysentery has a short incubation period (1-7 days, usually 48 hours). The onset and clinical course are variable and are largely determined by the virulence of the infecting strain.
• The clinical manifestations of shigellosis vary from asymptomatic to severe forms of the disease. The main clinical features are frequent passage of loose, scanty feces containing blood and mucus, along with abdominal cramps and tenesmus.
• Fever and vomiting may be present. Infection is usually self-limited, although antibiotic treatment is recommended to reduce the risk of secondary spread to family members and other contacts. In dysentery caused by S. dysenteria type 1, patients experience more severe symptoms.

“Role of viruses in causing infectious diseases: Questions answered”

Question 12. Pathogenesis of E.coli.
Answer:

Pathogenesis Esch. coli forms a part of the normal intestinal flora of man and animal. There are four major types of clinical syndromes which are caused by Esch. coli:

1. Urinary, Tract Infection
2. Diarrhea
3. Pyogenic Infections, And
4. Septicaemia.

1. Urinary Tract: Infection Esch. coli is the most common organism responsible for urinary tract infection (UTI). Esch, coli that cause UTI often originates in the intestine of the patient.

2. Diarrhoea Esch. coli causing diarrhoeal diseases are of four groups. They produce
diarrhea with different pathogenic mechanisms.

1. Enteropathogenic Esch, coli (EPEC): EPEC adheres tightly to enterocytes, leading to inflammatory reactions and epithelial degenerate changes.
2. Enterotoxigemic Esch. coli (ETEC): These are the strains that form a heat-labile enterotoxin (LT) a heat-stable enterotoxin (ST) or both. They are now known to be a major cause of diarrhea in children in developing countries and are the most important cause of travellers diarrhea. The name travelers diarrhea refers to diarrhea in persons from developed countries within a few days of their visit to one of the developing countries.
3. Enteroinvasive Esch. coli (EIEC): Some strains of Esch. coli invade the intestinal epithelial cells as do dysentery bacilli and produce disease identical to shigella dysentery. These have been named enteroinvasive Esch. coli (EIEC). On instillation into the eyes of guinea pigs, EIEC cause keratoconjunctivitis, This diagnostic test for EIEC is called Sereny test.
4. Enterohaemorrhagic Esch coli (EHEC) or Verocytotorin-producing Esch, coli (VTEC) hemorrhagic These strains cause haemolytic uraemic syndrome (HUS). The toxin responsible is called Verotoxin’ because of its effect Vero cells in culture.

3. Pyogenic Infections Esch. coli may cause wound infection, peritonitis, cholecystitis, and neonatal meningitis. It is an important cause of neonatal meningitis.

4. Septicaemia Esch. coli is a very common cause of septicaerria in many hospitals. This condition usually occurs in debilitated patients and mortality is very high.

“How do pathogenic organisms invade the human body? FAQ explained”

Question 13. Difference between Amoebic and Bacillary dysentery.
Answer:

Question 14. Pathogenesis of diarrhea.
Answer:

Diarrhoea Esch. coli causing diarrhoeal diseases are of four groups. They produce diarrhea with different pathogenic mechanisms.

Enteropathogenic Esch, coli (EPEC): EPEC adheres tightly to enterocytes, leading to inflammatory reactions and epithelial degenerate changes.

Enterotoxigemic Esch. coli (ETEC) These are the strains that form a heat-labile enterotoxin (LT) a heat-stable enterotoxin (ST) or both. They are now known to be a major cause of diarrhea in children in developing countries and are the most important cause of travelers diarrhea. The name travelers’ diarrhea refers to diarrhea in persons from developed countries within a few days of their visit to one of the developing countries.

Enteroinvasive Esch. coli (EIEC): Some strains of Esch. coli invade the intestinal epithelial cells as do dysentery bacilli and produce disease identical to shigella dysentery. These have been named enteroinvasive Esch. coli (EIEC). On instillation into the eyes of guinea pigs, EIEC causes keratoconjunctivitis, This diagnostic test for EIEC is called the Sereny test.

Enterohaemorrhagic Esch coli (EHEC) or Verocytotorin producing Esch, coli (VTEC) hemorrhagic These strains cause hemolytic uraemic syndrome (HUS). Toxin responsible is called Verotoxin’ because of its effect Vero cells in culture.

Question 15. Enlist organisms causing diarrhea
Answer:

Bacteria

• Vibrio cholera
• V. parahaemolyticus
• Escherichia coti (ETEC, EPEC) – Cryptosporidium panrum
• Salmonella Enteritidis
• S. Typhimurium
• Other Salmonella sp.
• Campylobacter sp.
• Yersinia enterocolitica
• Shigella sp.
• Clostridium perfringens
• C. difficile
• Staphylococcus aureus
• Bacillus cereus
• Aeromonas hydrophilia
• Plesiomonas shigelloides

Viruses

• Rotavirus
• Astrovirus
• Calicivirus
• Norwalk virus
• Adenovirus

Protozoa

• Entamoeba histolytica
• Oiardia lambda
• Isospora belli

Cestodes: Hymenolepis nana

Nematodes

• Trichuris trichiura
• Strongyloides stercoralis
• Ascaris lumbricoides
• Hookworms

Trematodes: Schistosoma mansoni

“Early warning signs of gaps in understanding pathogenic organism basics: Common questions”

Question 16. Write a short note on laboratory diagnosis of diarrhea.
Answer:

Laboratory Diagnosis

1. Collection of Specimens: In most cases the stool is sent for bacterial culture. Because there are many other potential pathogens, the laboratory must be informed which tests to perform.
2. Direct Microscopy: Microscopic examination of the stool may reveal white blood cells if the patient has inflammatory diarrhea. The bacterial pathogen may be visible on direct microscopic examination of the stool.
   • In general, a wet film of a concentrate of the feces should be examined for protozoa, protozoal cysts, and helminth ova, and a stained film for the oocysts of Cryptosporidium.
3. Culture: Selective and differential culture media are commonly used to attempt to identify bacterial pathogens in stool. The differential aspect of the media often allows differentiation of bacterial species based on colony morphology the differences in colony appearance are usually due to different biochemical characteristics of the organisms.
   • Vibrios Culture: Selective media such as TCBS or bile salt agar are used. Culture plates are incubated at 37°C for 24-48 hours. Vibrio parahaemolyticus is a halophilic vibrio in media containing sodium chloride.
   • Vibrios Identification: Identification of isolates is done by colony morphology, biochemical reactions
     and slide agglutination test.
     1. Esch. coli
     2. ETEC
     3. EPEC
     4. EIEC
     5. EAEC
4. Esch. coli Culture: Cuture is done on blood agar and MacConkey’s agar. These media are incubated at 37°C for 24 hours.
5. Esch. coli Identification: Identification of isolates is done by colony morphology, biochemical reactions, slide agglutination with antisera. For the identification of EIEC strains Sereny test is used. Another method for the identification of these strains is invasion of cultured HeLa cells.

Production of verocytotoxin (VT) is confirmed by testing the strains on Vero cells, in which they cause cytopathic effects.

Question 17. Blood Culture.
Answer:

A blood culture is a medical laboratory test used to detect bacteria or fungi in a person’s blood. Blood is normally sterile, and the presence of microbes in the blood often indicates a serious bloodstream infection such as a bacteremia, or fungemia, that can result in sepsis.

• The test involves drawing the blood into bottles containing chemicals that encourage microbial growth, which are then placed in an incubator for several days to allow the organisms to multiply.
• If microbial growth is detected, a Gram stain is made from the blood culture bottle to confirm that bacteria are present and to provide a preliminary identification.
• The blood is then inoculated onto an agar plate to isolate the organisms for further testing. A positive Gram stain from a blood culture is considered a critical result and must immediately be reported to the clinician.
• To ensure accurate results, blood cultures are drawn using sterile technique. If the sample is contaminated with skin flora, the person will appear to have those organisms in their blood.
• When a blood culture is performed, it is usually drawn in at least two different sets (one set of bottles from each arm) so that contamination is easier to detect. If an organism only appears in one of the two sets, it is more likely to be a contaminant.
• When a patient shows signs or symptoms of a systemic infection, results from a blood culture can verify that an infection is present, and they can identify the type (or types) of microorganism that is responsible for the infection.
• For example, blood tests can identify the causative organisms in severe pneumonia, puerperal fever, pelvic inflammatory disease, neonatal epiglottitis, sepsis, and fever of unknown origin (FUO). However, negative growths do not exclude infection.

Question 18. Blood smear
Answer:

A blood sample is used to look for abnormalities in the number and shape of blood cells, presence of parasites. blood smear, also referred to as a peripheral smear for morphology, is an important test for evaluating blood-related problems, such as those in red blood cells, white blood cells, or platelets.

It has a wide range of uses, including distinguishing viral infections from bacterial
infections, evaluating anemia, looking for causes of jaundice, and even diagnosing malaria. Unlike automated tests (such as a CBC), a technician or physician looks at a blood smear under a microscope in order to detect a wide range of changes that give clues to underlying diseases.

Blood Smear Purpose Of Test: A blood smear involves looking at a sample of blood under the microscope after applying special stains and looking for abnormalities or changes in red blood cells, white blood cells, and platelets.

There are many reasons why your doctor may order a blood smear. Some of these include:

• To further evaluate abnormalities found on a complete blood count (CBC) such as a high or low red blood cell count, white blood cell count, or platelet count.
• To evaluate an infection (identifying the types of white blood cells present can help determine if an infection is viral, bacterial, or parasitic, as well as the severity)
• To look for causes of unexplained jaundice
• As part of a workup for people who have unexplained weight loss (defined as a loss of 5 percent of body weight over a 6 month period without trying)
• To evaluate symptoms of lightheadedness and palor (paleness)
• To look for causes of petechiae, bruising, or excess bleeding
• With a low platelet count, to determine if the cause is increased degradation or decreased production (based on the size)
• To investigate findings suspicious for blood-related cancers
• To look for malaria
• To confirm sickle cell disease
• To evaluate symptoms of bone pain
• To look for causes of enlargement of the spleen, liver, or lymph nodes.

A blood smear looks for the numbers and characteristics of the three types of blood cells:

1. Red blood cells (RBCs) are the cells that transport oxygen to the tissues
2. White blood cells (WBCs) are cells that fight infection among several other functions
3. Platelets are cell fragments that play an important role in blood clotting.

“Asymptomatic vs symptomatic effects of ignoring pathogenic risks: Q&A”

Question 19. Enumerate the organism causing urinary track infection.
Answer:

E. coli and coliforms account for the large majority of naturally acquired urinary tract
infections. Those acquired in the hospital, following instrumentation, are more often caused by other bacteria such as Pseudomonas and Proteus.

The most frequently encountered O serotypes of E. coli in UTI include O1, O2, O4, O6, O7, O18, and O75. These are also known as nephritogenic strains. E. coli that cause UTI often originate in the gut of the patient. The bacteria may gain access to the urinary tract by the ascending or the hematogenous route.

1. Other members of the family Enterobacteriaceae that usually cause UTI are Klebsiella, Proteus, and Citrobacter, and those that rarely produce UTI are Salmonellae, Edwardsiellae, and Enterobacter.
2. The gram-positive organisms that can cause UTI are Staphylococcus aureus, coagulase-negative staphylococci, Streptococcus faecalis, S. pyogenes, S. agalactiae, S. milleri, other streptococci, and anaerobic streptococci.
3. Rarely, Gardnerella vaginalis may cause UTI.
4. Candida albicans may cause UTI in diabetic and immunocompromised patients.
5. The hospital-associated infection following instrumentation and catheterization is mostly caused by Pseudomonas and Proteus.

Question 20. Write down the laboratory diagnosis of Urinary track infection (UTI).
Answer:

Laboratory Diagnosis: Urinary Tract Infection: Normal urine is sterile, but during voiding may become contaminated with commensals of genital

1. Specimen Collection Midstream urine specimen (MSU): collected preferably prior to administration of antibiotics.
   • Specimen is collected in a sterile container. (Before collecting a sample, genitalia should be cleaned with soap and water and men are instructed to retract the foreskin of glans penis whereas women should keep the labia apart.
   • (The first portion of urine is allowed to pass, then without interrupting the urine low, mid-portion of the stream is collected. The first portion of urine adequately lushes out the normal urethral flora.)
   • Catheter specimen: Urine should be collected directly from the catheter and not from the collection bag, The catheter should hot-touch the container. Although a catheter specimen yields excellent results but catheterization to obtain urine is not justified because of risk of introducing infection.
   • Urine specimens from infants: A clean catch specimen after cleansing of genitalia is preferred. 2. Transport As urine is a good culture medium, specimens after collection should reach the laboratory with minimum delay, if it is not possible, the specimen is to be refrigerated at 4°C.
2. Laboratory Methods Part of the specimen is used for bacteriological culture and the rest is examined immediately under the microscope.
   • Microscopy Urine is centrifuged and the deposit is examined under the microscope to detect pus cells, erythrocytes, epithelial cells, and bacteria.
   • Culture Most laboratories use a semiquantitative method (standard loop technique) for the culture of urine specimens.
   • Identification The organisms are identified by colony characters Grams staining, motility, biochemical reactions and slide agglutination test.“
   • Antibiotic sensitivity test Esch. coli and other common urinary pathogens develop multiple drug resistance. Antibiotic sensitivity is necessary to administer proper antibiotics.

Question 21. Widal Test.
Answer:

Widal test: In the Widal test used for the diagnosis of enteric fever, two types of antigens are used: the flagellar antigens (H) and somatic (O) antigens. H antigen is a formolised suspension of the organisms which combined with its antibody,  forms large, loose, and fluffy clumps resembling wisps of cotton wool.

• Conical Dreyer’s tubes are used for H agglutination. O (somatic) antigen is prepared by treating the bacterial suspension with alcohol.
• It forms tight, compact deposits resembling chalk powder at the base of round-bottomed (Felix) tubes on combination with antibody. Agglutinated bacilli spread out in a disk-like pattern at the bottom of the tube, whereas, the negative reaction shows a compact button-like deposit.

“Can targeted interventions improve outcomes using pathogenic knowledge? FAQs provided”

Question 22. Describe the normal microbial flora of different body parts.
Answer:

Normal Flora refers to the population of microorganisms that inhabit the skin and mucous membranes of normal human body. A healthy fetus in utero is free from micoorganisms. During birth the infant is exposed to vaginal flora.

Within a few hours of birth, oral and nasopharyngeal flora develops and in a day or two resident flora of the lower intestine appears. The normal microbial flora is more or less constant for each species of animal.

1. Normal Flora Of The Skin: The skin contains 102 to 101 organisms per cm2. Bathing has little effect on the resident flora of the skin. Staph epidermidis and diphtheroids are numerous and most constant in the skin. Other microorganisms include Peptococcus, Str viridans, Enterococcus, Micrococcus, Esch. coli, Proteus, Candida albicans, and Propionibacterium aono. Penicillin-resistant staphylococci are seen in individuals working in hospitals.
2. Normal Flora Of The Conjunctiva: The conjunctiva is relatively free from bacteria due to the flushing action of tears and due to the presence of lysozyme in it. The predominant organisms are Corynebacterium xerosis, Staph. epidermidis, Moraxella species, and non-hemolytic streptococci.
3. Normal Flora Of The Nose And Nasopharynx: The flora of the nose harbors diphtheroids, staphylococci, streptococci, and Haemophilus species. The nasopharynx of the infant is sterile at birth but, within 2-3 days after birth, acquires the flora carried by the mother and the attendants. The nasopharynx is a natural habitat of the common pathogens that cause infections of the nose, throat, bronchi, and lungs.
4. Normal Flora Of The Mouth: The mouth contains micrococci, Gram-positive aerobic spore-bearing bacilli, coliforms, Proteus, and lactobacilli. The gum pockets between the teeth have a wide spectrum of anaerobic bacilli, anaerobic micrococci, microaerophilic and anaerobic streptococci, vibrios, fusiform bacilli.
   • Corynebacterium species, actinomyces, mycoplasma and Bacteroides are all found in varying extents. The mouth of an infant is not sterile at birth. It generally contains the same organisms as those present in the mother’s vagina i.e. a mixture of micrococci, streptococci, coliform bacilli, and Doderlien’s bacilli. These organisms diminish in number during the first 2-5 days after birth and are replaced by the bacteria present in the mouth of the mother.
5. Normal Flora Of The Upper Respiratory Tract: Within 12 hours after birth alpha haemolytic streptococci are present in the upper respiratory tract. They become the dominant organism of the oropharynx and remain so for life. In the pharynx and trachea, flora is similar to that of the mouth. A few bacteria are present in normal bronchi, but smaller bronchi and alveoli are normally sterile.
6. Normal Flora Of The Gastrointestinal Tract: The gastrointestinal tract of the foetus in utero is sterile. It becomes contaminated with organisms shortly after birth. In breastfed infants, the intestine contains lactobacilli, enterococci, colon bacilli, and staphylococci.
   • In bottle-fed infants, the intestine contains Leptotrichia, anaerobic lactobacilli, colon bacilli, and aerobic and anaerobic spore-bearing organisms. Due to the low pH of the stomach, it is virtually sterile except soon after eating, As the acidic pH of the stomach becomes alkaline in the intestine, the number of bacteria increases progressively beyond the duodenum to the colon. The bacterial count is low in the small intestine compared to that in the large intestine.

Question 23. Describe the Organisms causing sore throat.
Answer:

Sore throat is essentially an acute tonsillitis or pharyngitis. It is characterized by  edness and edema of the mucosa, exudation of tonsils, pseudomembrane formation, edema of the uvula, gray coating of tongue, and enlargement of cervical lymph nodes.

Causative agents of sore throat are given:

Bacteria

• Streptococcus β-hemolytic group A and occasionally groups C and G
• Corynebacterium diphtheriae
• Haemophilus influenza
• Bordetella pertussis
• Neisseria gonorrhoeae
• Treponema vincentii
• Leptotrichia buccalis

Fungi

• Candida albicans
• C. Viruses
• Epstein-Barr virus
• Adenoviruses
• Coxsackievirus A

Question 24. Write a Short Note on Food poising.
Answer:

The term bacterial food poisoning is restricted to acute gastroenteritis due to the presence of bacteria, usually in large numbers, or their products in food. It is of three types.

Infective type: In this type, the multiplication of bacteria occurs in vivo when infective doses of microorganisms are ingested with food. The incubation period is generally 8 to 24 hours. A typical example of this type of food poisoning is by Salmonella.

Toxic type: In this type, the disease follows ingestion of food with preformed toxin. The incubation period is short (2 to 6 hours). An example is staphylococcal food poisoning.

Causative agents of food poisoning

1. Infectlve type

• Salmonella typhimurium
• S. Enteritidis
• S. Heidelberg
• S. Indiana
• S. Newport
• S. Dublin
• Vibrio parahaemolyticus
• Campylobacter jejuni

2. Toxic type

• Staphylococcus aureus.
• Bacillus cereus
• Clostridium botulinum

3. Infectlve—toxic type: Clostridium perfringens

Infective-toxic type: In this type, bacteria release the toxin in the bowel. The incubation period is 6 to 12 hours. A typical example is C. perfringens food poisoning. For the laboratory diagnosis. It has also been described earlier under “Laboratory Diagnosis of Diarrhea”.

“Differential applications of opportunistic vs primary pathogens: Questions answered”

Question 25. Describe life cycle of a malarial parasite.
Answer:

Malaria is a mosquito-borne infectious disease of humans. Malaria is caused by a parasite that is passed from one human to another by the bite of infected Anopheles mosquitoes.

After infection, the parasites (called sporozoites) travel through the bloodstream to the liver, where they mature and release another form, the merozoites which introduces the protists via its saliva into the circulatory system, and ultimately to the liver where they mature and reproduce.

Intermediate host: human

• Final host: mosquito
• Infective stage: sporozoite
• Infective way: mosquito bites skin of human
• Parasitic position: liver and red blood cells
• Transmitted stage: gametocytes
• Schizogonic cycle in red cells: 48 hrs/P.v
• Sporozoite: tachysporozite and bradysporozite

“Difference between bacteria and viruses in pathogenic organisms: Q&A explained”

Question 26. Write a short note on lab diagnosis of malaria.
Answer:

Lab Diagnosis of Malaria: Method used to diagnose

1. Microscopy Serology
2. Rapid Diagnostic Tests
3. Molecular biology method (PCR)

Microscopy

• Gold standard
• Highly sensitive, specific
• Laboratory diagnosis of malaria can by made through microscopic examination of thick or thin blood smear.
• Thick smears are used for screening purposes Thin smears are for morphological detail and species identification.
• The mainstay of malaria diagnosis has been the microscopic examination of blood, utilizing blood films Although blood is the sample most frequently used to make a diagnosis, both saliva and urine have been investigated as alternative, less invasive specimens.
• More recently, modern techniques utilizing antigen tests or polymerase chain reactions have been discovered, though these are not widely implemented in malaria-endemic regions.
• Areas that cannot afford laboratory diagnostic tests often use only a history of subjective fever as the indication to treat for malaria.

Question 27. Draw a well-labeled diagram of the embryonated egg.
Answer:

Question 28. Draw a good diagram of HIV viruses.
Answer:

“Most common complications of poorly understood pathogenic organisms: FAQs”

Question 29. Write down the causes and Routes and Modes of HIV infection.
Answer:

Routes of Transmission: Virus is present in the blood, semen, and cervical and vaginal secretions, and these sources are important in transmission. HIV is spread only by three modes

1. Sexual contact with infected persons (heterosexual or homosexual)
2. By blood and blood products
3. From infected mother to babies (intrapartum, perinatal, postnatal).

The modes of transmission of HIV and their relative risks are shown in Tables

1. Sexual Intercourse: HIV is primarily a sexually transmitted infection. Heterosexual transfer of virus is the route by which the great majority of infections are spread, accounting for 90 percent of the global total.

• Both sexes are affected equally. Transmission in developing countries is almost always heterosexual and can take place in both directions.
• The presence of other sexually transmitted diseases such as syphilis, gonorrhea, or herpes simplex type 2 increases the risk of sexual HIV transmission as much as a hundred-fold.
• Sex workers are at high risk due to their large number of partners. Most early studies established that unprotected anal intercourse was a particular risk, especially to the passive, receptive partner. The risk increases in proportion to the number of sexual encounters with different partners.

2. Blood and Blood Products: Transfusion of infectious blood or blood products is an effective route for viral transmission.

• Contaminated Needles
• This is particularly relevant in drug addicts who share syringes and needles. Drug and sexual routes merge when misusers support their habit by prostitution.
• The use of unsterile syringes and needles by qualified and unqualified health workers makes iatrogenic.
• Contamination of eyes and mucous membranes is another possible route, but this is seldom confirmed.
• Tattoo needles and contaminated inks are other potential means by which HIV can be transmitted.

3. Mother-to-Child Transmission: Transmission of infection from mother to baby can take place before, during, or after birth.

Mother-to-infant transmission rates vary from 13 to 40 percent in untreated women Infants can become infected in utero, during the birth process, or, more commonly, through breastfeeding. Transmission during breastfeeding usually occurs early (by 6 months).

Question 30. Write the stages of the HIV infection
Answer:

The natural evolution of HIV infection can be considered in the following stages.

• The acute seroconversion illness resembles glandular fever, with adenopathy and flu-like symptoms. Within 3-6 weeks of infection with HIV, about 50 percent of persons experience low grade fever, malaise, headache, lymphadenopathy, sometimes with rash and arthropathy resembling glandular fever.
• During this period there is a very high level of virus replication occurring in CD4+ cells. Tests for HIV antibodies are usually negative at the onset of the illness but become positive during its course. Hence this syndrome has been called ‘seroconversion’ illness.

“Why are pathogenic organisms often misunderstood in practice? Questions answered”

Asymptomatic or Latent Infection: A clinically asymptomatic or “latent” period follows the acute infection. During this time, there is a high level of ongoing viral replication.

They show positive HIV antibody tests during this phase and are infectious. The infection progresses in the course of time through various stages, including CD4 lymphocytopenia, minor opportunistic infections, persistent generalized lymphadenopathy, and AIDS-related complex (ARC), ultimately terminating in full-blown AIDS, with its characteristic infections and malignancies. The time from infection to death may be as long as 10 years and is inevitable in 70 percent of infected persons.

Persistent Generalized Lymphadenopathy (PGL ): Persistent generalized lymphadenopathy (PGL) is present in 25-30 percent of patients who are otherwise asymptomatic. This has been defined as the presence of enlarged lymph nodes, at least 1 cm in diameter, in two or more noncontiguous extra inguinal sites, that persist for at least three months, in the absence of any current illness or medication that may cause lymphadenopathy. The rate of progression of patients with PGL to AIDS is no greater than in those without adenopathy. This by itself is benign but the cases may progress to ARC or AIDS.

AIDS Related Complex (ARC): This group includes patients with considerable immunodeficiency, suffering from various constitutional symptoms or minor opportunistic infections. The typical constitutional symptoms are fatigue, unexplained fever, persistent diarrhea, and marked weight loss of more than 10 percent of body weight. ARC patients are usually severely ill and many of them progress to AIDS in a few months. With no treatment, the interval between primary infection with HIV and the first appearance of clinical disease is usually long in adults, averaging about 8-10 years. Death occurs about 2 years later.

AIDS: This is the end-stage disease representing the irreversible breakdown of immune defense mechanisms, leaving the patient prey to progressive opportunistic infections and malignancies. AIDS may be manifested in several different ways, including lymphadenopathy and fever, opportunistic infections, malignancies, and AIDS-related dementia.

Question 31. Pathogenesis of HIV and AIDS.
Answer:

Pathogenesis of HIV and AIDS

“Cost of ignoring pathogenic risks vs benefits of systematic prevention: Q&A”

Question 32. Write down the laboratory diagnosis of HIV/ Aids.
Answer:

Laboratory Diagnosis: Specific Tests for HIV Infections

1. Antigen detection: The p24 antigen is the earliest virus marker to appear in the blood. ELISA can be used for the detection of this antigen. Virus isolation is an important test for diagnosis in the window period when antibodies are absent in the serum of a patient.
2. Virus isolation: For diagnosis, the virus is not routinely isolated. It can be isolated from CD4 lymphocytes of peripheral blood, bone marrow, and serum. Virus isolation is an important test for diagnosis in the window period when antibodies are absent in serum of the patient.
3. Detection of viral nucleic acid: Viral nucleic acid can be detected by polymerase chain reaction (PCR). The test is highly sensitive and specific. It is also useful for diagnosis in the window period.
4. Antibody detection: Demonstration of antibodies is the simplest and most commonly employed technique for diagnosis. It may take several weeks to months for antibodies to appear after infection. HIV-infected persons remain negative for antibodies during window period, when initial viral replication takes place for about 2-3 weeks. There are two types of serological tests-screening and supplemental.

Laboratory Diagnosis Screening tests

1. ELISA test: ELISA is the method most commonly used. It is a highly sensitive and specific test. It is an extremely good screening test and most laboratories use a commercial ELISA kit that contains both HIV-1 and HIV-2. Saliva is an acceptable alternative to serum for antibody testing by ELISA.

2. Rapid tests: These tests take less than 30 minutes and do not require expensive
equipment. The rapid tests include dot-blot assay, particle agglutination, HIV spot, and comb tests.

3. Simple tests: They take 1-2 hours and do not require expensive equipment.

Laboratory Diagnosis Supplemental test

Western blot test: In this test, HIV proteins are separated and these proteins are blotted onto strips of nitrocellulose paper. These strips are reacted with test sera. Antibodies to HIV proteins, if present in test serum, combine with different fragments of HIV. The position of the color band on the strip indicates the fragment of antigen with which antibodies have reacted.

Question 33. The life cycle of Ascaris Lumbricoid ( Round Worm).
Answer:

Life Cycle Ascaris lumbricoides pass its life cycle in only one host, man. No intermediate host is required. Man is the only definitive host. Adult worms live the jejunum of man. Fertilized eggs containing the unsegmented ova are passed in the feces. These eggs are not immediately infective to man.

Egg undergo development in soil. A rhabditiform larva is developed from an unsegmented ovum and undergoes first molting within the eggshell. These eggs containing rhabditiform larvae are pathogenic to man. Man acquires infection by ingestion of food, drink of raw vegetables contaminated with eggs containing rhabditiform larvae (embryonated eggs).

In the upper Part of the small intestine (duodenum), rhabditiform larvae are liberated from the embryonated eggs. These newly hatched larvae then burrow their way through the mucous membrane of the small intestine and are carried by the portal circulation to the liver.

They then pass out of the liver and via right heart enter the pulmonary circulation. In the lungs they grow much bigger in size and moult twice. They break through the capillary wall and reach the lung alveoli. From the larvae crawl up the bronchi and trachea and propelled into the larynx and pharynx and are Srallowed.

They pass down the esophagus to the stomach and localize in the upper part of the small intestine, their normal abode. Another molting takes place. The larvae grow into adult worms and sexual maturity occurs. The gravid female begins to discharge eggs in the stool and the life cycle is again repeated.

Question 34. List 4 DNA viruses and 4 RNA viruses.
Answer:

DNA Viruses: Sometimes referred to as the happy viruses

• Herpes
• Hepadna
• 4/3 Adeno
• 4/3 Papova
• 4/3 Parvo
• 4/3 Pox
• 4/3 Most

DNA viruses are double-stranded, show icosahedral symmetry, and replicate in the nucleus.

1. Parvoviridae Family: Three genera have been described: Parvovirus, Adenosatellovirus, and Densovirus.

2. Hepadnaviridae Family: This consists of the human hepatitis type B virus and related viruses of animals and birds. (The name comes from hepa = liver, and DNA for DNA core). Three viral types are known that infect mammals (humans, woodchucks, and ground squirrels) and another that infects ducks.

3. Papovaviridae Family: Two genera have been recognized—Papillomavirus and Polyomavirus. Papillomavirus are also a former member of the Papovaviridae family. Polyomaviruses were formerly a part of the Papovaviridae family before it was split into two families.

4. Adenoviridae Family: Members have been classified into two genera: Mastadenovirus (mammalian adenoviruses) and Aviadenovirus (adenoviruses of birds)

5. Poxviridae Family: The family is divided into several genera. All poxviruses tend to produce skin lesions. Some are pathogenic for humans (smallpox, vaccinia, molluscum contagiosum); others that are pathogenic for animals can infect humans (cowpox, monkeypox).

RNA Viruses: There are certain generalities about RNA viruses, most of which are the opposite of DNA viruses. Most RNA viruses are single-stranded (half are positive [+1 stranded, half negative [-1), enveloped, show helical capsid symmetry, and replicate in the cytoplasm

• 4/3 Toga
• 4/3 Corona
• 4/3 Retro
• 4/3 Picorna
• 4/3 Calici
• 4/3 Reo
• 4/3 Orthomyxo
• 4/3 Paramyxo
• 4/3 Rhabdo
• 4/3 Bunya
• 4/3 Arena
• 4/3 Fibo.

Paramyxoviridae Family: Three genera have been recognised

1. Paramyxovirus which consists of the Newcastle disease virus, mumps virus and
   parainfluenza viruses of humans, other mammals, and birds.
2. Morbillivirus, containing measles, canine distemper, rinderpest, and related viruses.
3. Pneumovirus, containing respiratory syncytial virus of humans and related viruses.

Paramyxoviridae Family: Three genera have been described

1. Alphavirus, consisting of viruses formerly classified as Group A arboviruses.
2. Rubivirus, consisting of the rubella virus has no arthropod vector.
3. Pestivirus, consisting of the mucosal disease virus, hog cholera virus, and related viruses.
4. Coronaviridae Family Only one genus of Coronavirus has been recognized.

Members include human coronavirus causing upper respiratory disease, avian infectious bronchitis virus, calf neonatal diarrhea coronavirus, murine hepatitis virus, and related viruses. Most human coronaviruses cause mild acute upper respiratory tract illnesses (colds) but a new coronavirus identified in 2003 causes a severe acute respiratory syndrome (SARS). Toroviruses, which cause gastroenteritis, form a distinct genus.

Reoviridae Family: Icosahedral, nonenveloped viruses, medium-sized (6080 nm), with double-layered capsids. The genome consists of double-stranded RNA in 10-12 pieces. Three genera have been recognised.

1. Reovirus, containing reoviruses from humans, other mammals, and birds.
2. Orbivirus, containing several species of arboviruses such as bluetongue virus, and African horse sickness virus.
3. Coltivirus includes the Colorado tick fever virus of humans.
4. Rotavirus including human rotaviruses, calf diarrhea virus, and related agents. Other genera may have to be defined to include plant and insect viruses belonging to this family.

“Is pathogen-related risk reversible if addressed promptly? Answer provided”

Question 35. General Characteristics or properties of Viruses.
Answer:

Viruses are the smallest known infective agents and are perhaps the simplest form of life known. Viruses do not possess a cellular organization and they do not fall strictly into the category of unicellular microorganisms.

Even the simplest of microorganisms are cells enclosed within a cell wall, containing both types of nucleic acid (DNA and RNA), synthesizing their own macromolecular constituents and multiplying by binary fission.

Main properties of viruses

1. Viruses do not have a cellular organization.
2. They contain only one type of nucleic acid, either DNA or RNA but never both.
3. They are obligate intracellular parasites.
4. They lack the enzymes necessary for protein and nucleic acid synthesis and are dependent
   for replication on the synthetic machinery of host cells.
5. They multiply by a complex process and not by
   binary fission.
6. They are unaffected by antibacterial antibiotics.

Question 36. Explain the various methods of the cultivation of viruses.
Answer:

Cultivation Of Viruses: Because viruses are obligate intracellular parasites, their growth requires susceptible host cells capable of replicating them. They cannot be grown on any inanimate culture medium. Three methods are employed for the cultivation of viruses:

1. Animal inoculation
2. Embryonated eggs
3. Cell culture.

1. Animal Inoculation: Uses of Animal Inoculation

1. Primary isolation of certain viruses
2. For the study of pathogenesis, immune response, and epidemiology of viral diseases
3. For the study of oncogenesis.

Monkeys: Monkeys were used for the isolation of the poliovirus but find only limited application in virology due to their cost and risk to handlers.

Mice: The use of white mice, pioneered by Theiler (1903) extended the scope of animal inoculation greatly. Infant (suckling) mice are very susceptible to coxsackie and arboviruses, many of which do not grow in any other system.

Mice may be inoculated by several routes— intracerebral, subcutaneous, intraperitoneal, or intranasal. The growth of the virus in inoculated animals may be indicated by death, disease, or visible lesions. The viruses are identified by testing for neutralization of their pathogenicity for animals, by standard antiviral sera.

2. EmbrYonated Eggs: The embryonated hen’s egg was first used for the cultivation of viruses by Goodpasture (1931) and the method was further developed by Burnet. The embryonated egg (8-11 day old) are inoculated by several routes for the cultivation of viruses such as chorioallantoic membrane (CAM), allantoic cavity, amniotic cavity, and yolk sac. After being inoculated, eggs are incubated for 2-9 days.

3. Tissue Culture: Three types of tissue cultures are available

1. Organ Culture: Small bits of organs can be maintained in vitro for days and weeks, preserving their original architecture and function. Organ cultures are useful for the isolation of some viruses which appear to be highly specialized parasites of certain organs. For example, the tracheal ring organ culture is employed for the isolation of coronavirus, a respiratory pathogen.
2. Explant Culture: Fragments of minced tissue can be grown as ‘explant’ embedded in plasma clots and was originally known as ‘tissue culture’. This method is now seldom employed in virology. Adenoid tissue explant cultures were used for the isolation of adenoviruses.
3. Cell Cultures: This is the type of culture routinely employed for growing viruses. Tissues are dissociated into the component cells by the action of proteolytic enzymes such as trypsin and mechanical shaking. The cells are washed, counted and suspended in a growth medium. Such media will enable most cell types to multiply with a division time of 24-48 hours.

“Success rate of interventions using modern pathogen techniques: FAQ”

Question 37. Classification of viruses.
Answer:

Classification Of Viruses: Viruses began to be classified into groups based on their physicochemical and structural features from the early 1950s. Nomenclature and classification are now the official responsibility of the International Committee on Taxonomy of Viruses.

Main Criteria Used for the Classification of Viruses:

1. Type of nucleic acid: Viruses are classified into two main divisions depending on the type of nucleic acid they possess: riboviruses are those containing RNA and deoxyriboviruses are those containing DNA.
2. Number of strands of nucleic acid: Single- or double-stranded, linear, circular, circular with breaks, segmented.
3. The polarity of the viral genome: RNA viruses in which the viral genome can be used directly as messenger RNA are by convention termed ‘positive-stranded’ and those for which a transcript has first to be made are termed ‘negative-stranded
4. The symmetry of the nucleocapsid.
5. The presence or absence of a lipid envelope

The post BSc Nursing 1st Year Microbiology Nursing Chapter 4 Pathogenic Organisms Question And Answers appeared first on BDS Notes.

Question 1. Sources of infection
Answer:

Infection and immunity involve interaction between the animal body (host) and the infecting microorganisms. The lodgement and multiplication of a parasite in or on the tissues of a host constitute infection. It does not invariably result in disease.

Sources Of Infection

1. Human beings
2. Animals
3. Insects
4. Soil and water
5. Food.

1. Human Beings: The most common source of infection for human beings is human beings themselves. The parasite may originate from a patient or carrier.

“Understanding infection control through FAQs: Q&A explained”

Humans serving as the microbial reservoir:

1. Acquisition of “strep” throat through touching
2. Hepatitis by blood transfusions
3. Gonorrhea, syphilis, and AIDS by sexual contact
4. Tuberculosis by coughing; and the common cold through sneezing.

2. Animals

• Reservoir hosts: Many pathogens are capable of causing infections in both human beings and animals. Therefore, animals may act as a source of infection of such organisms. These, animals serve to maintain the parasite in nature and act as a reservoir and they are, therefore, called reservoir hosts.
• Zoonosis: The diseases and infections, which are transmissible to man from animals are
  called zoonosis.
  • Examples of zoonotic diseases
• Bacterial: Anthrax, brucellosis, Question fever, leptospirosis, bovine tuberculosis, bubonic plague,
  Salmonella food poisoning.
• Viral: Rabies, yellow fever, cowpox, monkeypox.
• Protozoal: Leishmaniasis, toxoplasmosis, trypanosomiasis, babesiosis.
• Helminthic: Echinococcosis, taeniasis, trichinellosis.
• Fungal: Microsporum canis, Trichophyton verrucosum.

3. Insects:

Arthropod-Borne Diseases: Blood-sucking insects, such as mosquitos, ticks, mites, ies, and lice may transmit pathogens to human beings, and diseases so, caused are called arthropod-borne diseases.

Insects Vectors: Insects that transmit infections are called vectors. Vector-borne transmission can be of two types either mechanical (external) or biological (internal).

Mechanical vector: The disease agent is transmitted mechanically by the arthropod.

Mechanical vector Examples: Transmission of diarrhea, dysentery, typhoid, food poisoning, and trachoma by the house.

Biological vectors: Biological vectors are those in whom the pathogens multiply sufficiently or has undergone a developmental cycle. The interval between the time of entry of the pathogen into the vector and the vector becoming infective is called the extrinsic incubation period.

Biological vectors Examples: Aedes aegypti mosquito in yellow fever, Anopheles mosquito in malaria.

Reservoir hosts: Besides acting as vectors, some insects may also act as reservoir hosts (for example, ticks in relapsing fever and spotted fever). Infection is maintained in such insects by transovarial or transstadial passage.

4. Soil And Water

Soil: Some pathogens can survive in the soil for long periods.

Soil Examples

• Spores of tetanus and gas gangrene: Spores of tetanus and gas gangrene remain viable in the soil for several decades and serve as source of infection.
• Fungi and parasites: Fungi (causing mycetoma, sporotrichosis, histoplasmosis) and parasites such as roundworms and hookworms also survive in the soil and cause human infection.

Water: Water may act as the source of infection either due to contamination with pathogenic microorganisms (Shigella, Salmonella, Vibrio cholerae, poliomyelitis virus, hepatitis virus) or due the presence of aquatic vector (cyclops containing larvae of guinea worm infection).

5. Food: Contaminated food may act as source of infection of organisms causing food poisoning, gastroenteritits, diarrhea and dysentery.

“How does infection control impact patient safety? FAQ answered”

Question 2. Classification of infection.
Answer:

The lodgement and multiplication of a parasite in or on the tissues of a host constitute infection. It does not invariably result in disease.

Classification Of Infections: Infections may be classied in various ways

1. Primary infection: Initial infection with a parasite in a host is termed primary infection.
2. Reinfections: Subsequent infections by the same parasite in the host are termed reinfections.
3. Secondary infection: When a new parasite sets up an infection in a host whose resistance is lowered by a preexisting infectious disease, this is termed secondary infection.
4. Local infection: The term local infection (more appropriately local sepsis) indicates a condition where, due to infection or sepsis at localized sites such as appendix or tonsils, generalized effects are produced.
5. Cross-infection: When in a patient already suffering from a disease, a new infection is set up from another host or another external source, it is termed cross-infection.
6. Nosocomial infections: Cross-infections occurring in hospitals are called nosocomial infections (from Greek nosocomion hospital).
7. Iatrogenic infection: The term iatrogenic infection refers to physician induced infections resulting from investigative, therapeutic or other procedures.
8. In apparent infection: In apparent infection is one where clinical effects are not apparent.
9. Subclinical infection: The term subclinical infection is often used as a synonym to in apparent infection.
10. Atypical infection: Atypical infection is one in which the typical or characteristic clinical manifestations of the particular infectious disease are not present.
11. Acute infection: An infection which lasts for a relatively short time. (few days to few weeks). Example: Measles.
12. Chronic infection: An infection which lasts for a long time (over months and years). Example: TB.
13. Autoinfection: An infection that occurs between two sites on the same host.(worms)
14. Mixed infection: An infection caused by two or more organism.(bacterial vaginosis)
15. Masked infection: An infection is known to occur but the infectious agent cannot be demonstrated.
16. Oppurtunistic infection: An infection with organisms which are normally harmless but become pathogenic when the body’s defence mechanisms are compromised.

Question 3. Define carrier and its classification with examples.
Answer:

Carrier: A carrier is person who harbours or lodge of the microorganisms without suffering from any ill effect because of it. There are several types of carriers:

1. Convalescent carrier: An individual who has recovered from the infectious disease but continues to harbour or lodge large numbers of pathogen.
2. Healthy carrier: A healthy carrier is an individual who harbours or lodge the pathogen but is not ill.
3. Incubatory carrier: An incubatory carrier is an individual who is incubating the pathogen in large numbers but is not yet ill.
4. Temporary carriers: Convalescent, healthy, and incubatory carriers may harbour or lodge the pathogen for only a brief period (hours, days, or weeks) and lasts less than six months.
5. Chronic carriers: They harbour the pathogen for long periods (months, years, or life).
6. Contact carriers: The term contact carrier is applied to a person who acquires the pathogen from a patient.
7. Paradoxical carrier: This refers to a carrier who acquires the pathogens from another carrier.

Question 4. Modes of transmission of infection
Answer:

Modes Of Transmission Of Infection: Pathogenic organisms can spread from one host to another by a variety of mechanisms.

These include as follows:

Contact: Infection may be acquired by contact, which may be direct or indirect.

1. Direct contact: Diseases transmitted by direct contact include STD (sexually transmitted diseases), such as syphilis, gonorrhea, lymphogranuloma venereum, lymphogranuloma inguinale, trichomoniasis, herpes simplex type 2, hepatitis B and acquired immunodeciency syndrome (AIDS).
2. Indirect contact: Fomites: Indirect contact may be through the agency of fomites, which are inanimate objects, such as clothing, pencils or toys which may be contaminated by a pathogen from one person and act as a vehicle for its transmission to another.

Inhalation – Droplet nuclei: Respiratory infections, such as the common cold, influenza, measles, mumps, tuberculosis, and whooping cough are acquired by inhalation.

Ingestion

• Intestinal infections are generally acquired by the ingestion of food or drink contaminated by pathogens. Infection transmitted by ingestion may be waterborne (cholera), foodborne (food poisoning), or handborne (dysentery).
• Diseases transmitted by water and food include chiey infections of the alimentary tract, for example, acute diarrheas, typhoid fever, cholera, polio, hepatitis A, food poisoning, and intestinal parasites.

Inoculation: The disease agent may be inoculated directly into the skin or mucosa, for example, rabies virus deposited subcutaneously by dog bite, tetanus spores implanted in deep wounds, and arboviruses injected by insect vectors. Infection by inoculation may be iatrogenic when unsterile syringes and surgical equipment are employed. Hepatitis B and the human immunodeciency virus (HIV).

Insects – Vector-Borne: Vector is denied as an arthropod or any living carrier (for example: nail) that transports an infectious agent to a susceptible individual. In some diseases, blood-sucking insects play an important role in the spread of infection from one individual to another.

Congenital-Vertical Transmission: Some pathogens are able to cross the placental barrier and reach the fetus in utero. This is known as vertical transmission.

Congenital Examples: So-called TORCH agents (Toxoplasma gondii, rubella virus, cytomegalovirus, and herpes virus), varicella virus, syphilis, hepatitis B, Coxsackie B, and AIDS.

“Importance of studying infection control for BSc Nursing students: Questions explained”

Question 5. Aseptic techniques
Answer:

The methods which are used to prevent the access of microorganisms during the preparation of parenteral products and their testing are called ‘ Aseptic Techniques’. Aseptic techniques are used to reduce the risk of post-procedure infections and to minimize the exposure of healthcare providers to potentially infectious microorganisms. Aseptic techniques include practices performed just before, during, or after any invasive procedures.

• Good aseptic techniques can only be applied if one knows the possible sources of contamination. The various sources of contamination are – Atmosphere, which is contaminated with dust, droplet and droplet nuclei becomes the breeding ground of microorganism.
• The hands are a major means of transmitting infection. Coughing, sneezing, and spitting can cause contamination at a considerable distance. The cloths which absorb dust particles are also a source of contamination.
• A handkerchief is the richest source of contamination. The hair, which is constantly exposed to atmospheric dust is source of contamination. These dust particles are liberated from the hair during brushing and shaking of the head.
• The unsterile equipment. The working surface.

Question 6 Characteristics of an ideal disinfectant.
Answer:

Disinfectants: Chemicals that kill vegetative bacteria, fungi, viruses, and rarely bacterial spores.

1. It should have a wide spectrum of activity.
2. It should have fast action.
3. It should be able to destroy infectious agents in clean as well as dirty condition.
4. It should dissolve easily.
5. It should have high penetration power.
6. It should be non-toxic and non-irritant.
7. It should not stain tissues.
8. It should not have an unpleasant odour.

“Common challenges in understanding infection control effectively: FAQs provided”

Question 7. Define disinfection. Write down the applications of most commonly used disinfectants. Or Enumerate any 4 chemical disinfectants.
Answer:

Disinfectants: Chemicals that kill vegetative bacteria, fungi, viruses, and rarely bacterial spores.

The various chemical disinfectants are:

1. Phenol and Related compounds:

• Phenol also called carbolic acid is the first chemical agent used as an antiseptic introduced by
  Lord Joseph Lister (1854).
• Phenol causes cell membrane damage and cell lysis. Phenol(1%) has bactericidal action but it is readily absorbed by skin and mucous membranes and causes toxicity.
• Thus it has been restricted and has been replaced by chemically related compounds like cresol, chloroxylenol, and chlorohexidine which are widely used as antiseptics.

Cresol: It is used as a solution of cresol in soaps(Lysol). It is used for disinfection of infected glassware. In laboratory disinfection of excreta, cleaning floors of wards and operation theatres.

Chloroxylenol: It is active ingredient of Dettol.

Chlorohexidine: It is bactericidal at high dilution. It is an active ingredient of Savlon which is widely used in burns, wounds, pre-operative disinfection of skin, etc.

2. Halogens: Chloride and Iodine are used as disinfectants being strong oxidizing agents.

Iodine: Used as skin disinfectant in the form of iodophores. A tincture of iodine (1-2% iodine in 70% alcohol) is used for cleaning or disinfecting skin and treating skin injuries. It is virucidal, herbicidal, and active against Tubercle bacilli.

Chlorine: Used widely as water disinfectant(0.5 to 1.0 milligrams per liter of water is effective). Products containing calcium hypochlorite are used for sanitizing utensils in restaurants. Sodium hypochlorite is used as a disinfectant for laboratory gloves, linen, syringes, and reagent
bottles.

3. Aldehydes: Two aldehydes are of considerable importance:

Formaldehyde:

• It is bactericidal, sporicidal and virucidal.
• It can be used in gaseous form or an aqueous solution.
• The gaseous form of formaldehyde is used for disinfection of rooms and for fumigation of operation theatres.
• A 10% solution of formalin (Formaldehyde gas + methanol) is used for killing bacterial cultures and suspension, cleaning contaminated surfaces, metal instruments and preservation of tissues for histopathological examination.
• It is also used to sterilize bacterial vaccines and in preparation of toxoid from toxin.

Glutaraldehyde:

• It is more effective and less irritant (toxic) than formaldehyde.
• It is active against bacteria (especially tubercle bacilli) and their spores, fungi, and various types of viruses including HIV and Enteroviruses.
• Glidex(2% buffered solution) is a commercial preparation used to sterilize cystoscopes, bronchoscopes, rubber anesthetic tubes, thermometers, polythene tubing, etc.

4. Alcohols: Pure alcohol has no disinfecting property. Three kinds of alcohols used as disinfectants are

Ethyl alcohol(ethanol): EA in a concentration between 50-70% is effective against viruses.

Methyl alcohol(methanol): Effective against fungal spores but it is toxic to eyes. Used for treating cabinets and incubators affected by spores.

Isopropyl alcohol(50-70%): Better than ethyl alcohol in bactericidal property used for disinfection of clinical thermometers.

5. Dyes: Two groups of dyes (aniline dyes and acridines) have been extensively used as skin and wound antiseptics. Both these groups are bacteriostatic in high dilution but have low bactericidal activity.

Aniline dyes: Include malachite green, brilliant green, and crystal violet. They are used on skin and mucous membranes as antiseptics and have been also used for some fungal infections like oral thrush.

Acridine dyes: Includes acriflavine, proflavine, aminacrine and euflavine. They are bacteriostatic and used for treating wounds and for irrigation of bladder and vagina.

“Why is early learning of infection control critical for nursing success? Answered”

Question 8. Standard safety measures.
Answer:

Standard Safety Measures Definition: Standard safety measures standard precautions or universal precautions are simple set of effective practices designed to protect health workers and patients from infection with a range of bloodborne and other pathogens from both recognized and unrecognized sources.

These practices are used when caring for all patients regardless of diagnosis. These rules are:

1. Single-use disposable injection equipment.
2. Discard contaminated sharps immediately in puncture or leak-proof containers.
3. Do not recap needle or use the hand technique for recapping.
4. Do not wash or disinfect latex gloves.
5. Handle soiled linen correctly(cleaning with detergent and hot water).
6. Disinfect instruments and surface areas.
7. Hand hygiene/Hand washing: Hand hygiene is a major component of standard precautions and one of the most effective methods to prevent transmission of pathogens associated with health care.
   • Standard Safety Measures Technique:
     • Hand washing(40-60sec): Wet hands and apply soap; rub all surfaces rinse hands and dry thoroughly with a single use towel use towel to turn off the faucet.
     • Hand rubbing(20-30sec): Apply enough product to cover all areas of the hands and rub hands until dry.
     • Hand washing should be done
       1. Before and after any direct patient contact and between patients, whether or not gloves are worn.
       2. Immediately after gloves are removed.
       3. Before handling an invasive device.
       4. After touching blood, body fluids, secretion, excretions, non-intact skin, and contaminated items, even if gloves are worn.
       5. During patient care, when moving from a contaminated to a clean body site of the patient.
       6. After contact with inanimate objects in the immediate vicinity of the patient.
8. Wear Protective barriers: Gloves
   • Wear when touching blood, body fluids, secretions, excretions, mucus membranes, and nonintact skin.
   • Change between tasks and procedures on the same patient after contact with potentially infectious material.
   • Remove after use, before touching non-contaminated items and surfaces, and before going to another patient. Perform hand hygiene immediately after removal.
9. Prevention of needle sticks and injuries from other sharp instruments:
   • Use care when:
     • Handling needles, scalpels, and other sharp instruments or devices.
     • Cleaning used instruments.
     • Disposing of used needles and other sharp instruments.
10. Respiratory hygiene and cough etiquette: Persons with respiratory symptoms should apply source control measures: Cover their nose and mouth when coughing/ sneezing with tissue or mask, dispose of used tissues and masks, and perform hand hygiene after contact with respiratory secretions.
11. Enviromental cleaning: Use adequate procedures for the routine cleaning and disinfection of environmental and other frequently touched surfaces.
12. Linens:
    • Handle, transport, and process used linen in a manner which:
    • Prevents skin and mucus membrane exposures and contamination of clothing.
    • Avoid transfer of pathogens to other patients and or the environ
13. Waste disposal:
    • Ensure safe waste management.
    • Treat waste contaminated with blood, body fluids, secretions, and excretions as clinical waste, in accordance with local regulations.
    • Human tissues and laboratory waste that is directly associated with specimen processing should also be treated as clinical waste.
    • Discard single-use items properly.

Question 9. Define sterilisation. Describe in detail about sterilization by heat.
Answer:

Sterilization: Sterilization is a process by which an article, surface, or medium is freed of all living microorganisms including viruses, bacteria, their spores, and fungi.

Sterile: Material is heated in such a way that it contains no living organisms is said to be sterile.

Sterilization Physical methods:

1. Sunlight
2. Drying
3. Heat:
   • Dry heat: Red heat, Flaming, Incineration, Hot air oven.
   • Moist heat: Temperature below 100°C,
   • Temperature at 100°C
   • Temperature above 100°C
4. Filtration
5. Radiation
6. Sonic and Ultrasonic vibrations.

1. Sunlight: Direct sunlight has a sterilizing effect due to combined effect of UV rays and heat rays.

It has bactericidal effect and is one of the natural methods of sterilization of water in rivers, lakes, and tanks.

It is used to sterilize blankets, bedding, clothes, utensils, bedpans, etc. It is experimentally proved that typhoid bacilli when exposed to the sun on a piece of white drill cloth were killed in two hours, whereas bacteria remain alive in the dark even after six days.

2. Drying Or Desiccation: Moisture is essential for the growth of bacteria, so drying in air has deleterious effects on many bacteria. However, spores are unaffected and can remain alive for several month or even years. Therefore, it is not an ideal method of sterilization

3. Heat: Most common and one of the most effective methods of sterilization. Factors influencing sterilization by heat are

1. Nature of heat
   1. Dry
   2. Moist
2. Temperature and time
3. Number of organism present
4. Characteristics of organism such as species and sporing capacity.
5. Type of material from which organism is to be eradicated

Dry Heat: Dry heat kills microorganisms by causing destructive oxidation of essential cell constituents. The various methods of dry heat sterilization include:

1. Red Heat: It is used to sterilize metallic objects by holding them on the flame of a Bunsen burner till they are red hot.
   • Read Heat Example: inoculating wires, needles, forceps spatulas, etc.
2. Flaming: The article is passed over the flame of a Bunsen burner for few(3-4) times without allowing it to become red hot or stand too long.
   • Flaming Example: Glass slides, the mouth of culture tubes and bottles, cover slips, scalpels, blades, and needles.
3. Incineration: It is the process of complete burning of disposable wastes and some biomedical wastes in an electric furnace known as an “Incinerator”. It is the best method to decontaminate the destroying material and disposal of biochemical wastes. It is useful in the disposal of:
   • Soiled dressings, swabs.
   • Soiled paper and mouth wipes.
   • Animal carcasses.
   • Human anatomical waste.
   • Pathogenic materials.
4. Hot air oven: The hot air oven is made up of a double-walled steel chamber with the stout door.
   • The top or side contain a ventilator which is left open during sterilization, to disperse any
     moisture.
   • Air circulates within the oven by convention currents. This is most widely used method of sterilization by dry heat.

Moist heat: Sterilization by moist heat implies killing microorganisms by steam or hot water. Moist heat kills microorganisms by denaturation and coagulation of proteins. Moist heat in sterilization has 3 temperature ranges

• Temperature below 100°C
• Temperature at 100°C
• Temperature above 100°C

4. Filtration

• This method is used for sterilization of liquid substances or fluids such as sera and solutions of heat liable substances such as sugars, urea, enzyme, and antibiotics which get damaged by heat process. The method is also used for separation of bacteriophages and bacterial toxins from bacteria.
• The spore size is not less than 0.75m in diameter and it retains bacteria but allows viruses to pass
  through filtrate. Therefore filtered preparations are not safe and cannot be employed for clinical use.

5. Irradiation: Radiation used for sterilization is of two types Ionizing radiation, for example, X-rays, gamma rays, and high-speed electrons. Non-ionizing radiation, for example, ultraviolet light, and infrared light. These forms of radiation can be used to kill or inactivate microorganisms.

“Factors influencing success with infection control knowledge: Q&A”

Question 10. Describe the principle of an autoclave.
Answer:

Autoclave:

“An autoclave is a modified pressure cooker in which sterilization by saturated steam under high pressure is achieved (autoclaving)”. An autoclave may be horizontal or vertical. It is a double-walled or jacketed chamber (outer chamber) made up of stainless steel or gun metal with supporting frame.

• The steam circulates within the jacket and is supplied under high pressure to closed inner chamber where articles for sterilization are kept.
• One-fifth of the cylinder is filled with water, materials to be sterilized are kept inside, lid is closed and heater is put on. vThe safety valve is adjusted to required pressure (15psi/inch square).
• The boiling of water inside the chamber after some time results in steam which is allowed to escape with air mixture till the cylinder becomes air-free.
• The discharge tap is closed and the desired pressure inside in chamber is allowed to rise to the one chosen for autoclaving for a fixed time thus complete sterilization is achieved.
• One-fifth of the cylinder is filled with water, materials to be sterilized are kept inside, the lid is closed and the heater is put on. The safety valve is adjusted to the required pressure (15psi/inch square).

Read And Learn More: Bsc Nursing 1st Year Microbiology Previous year Question and Answers

• The boiling of water inside the chamber after some time results in steam which is allowed to escape with air mixture till the cylinder becomes air free.
• The discharge tap is closed and the desired pressure inside in chamber is allowed to rise to the one chosen for autoclaving for a fixed time thus complete sterilization is achieved.
• Satisfactory autoclaving or sterilization can be achieved at 15 pounds per square inch(psi) pressure which is equivalent to 121°C of temperature and the time of operation is 15-20 min.
• At this temperature, most of the heat-resistant spores are killed which cannot be achieved by other sterilization methods.
• However, sterilization can also be done at higher temperatures, at 126°C(20 lbs pressure/inch square) for 10 min or at 133°C(30 lbs pressure/inch2) for 3 min.
• Autoclaving is ideal method of destruction of bacterial spores. It is used to sterilize culture media, rubber goods, syringes, gowns, dressing, linen, gloves,
  etc.

Question 11. Categories of Biomedical waste.
Answer:

Biomedical Waste Definition: Biomedical waste means any solid or liquid waste that is generated during the diagnosis, treatment, or immunization of human beings or animals, in research activities, or in the production or testing of biological products.

“Steps to explain types of infection control: Hand hygiene vs sterilization: Q&A guide”

Question 12. Disposal of Biomedical waste.
Answer:

Disposal Of Biomedical Waste Definition: Biomedical waste means any solid or liquid waste that is generated during the diagnosis, treatment, or immunization of human beings or animals, in research activities, or in the production or testing of biological products.

Different methods of treatment and disposal are:

1. Incineration: Incineration is a method of treating waste that involves the combustion of the organic substances found in waste materials.

• The key difference between combustion and Incineration is that combustion includes the reaction between substances and oxygen, which produces energy, whereas incineration is the destruction of something via burning.
• However, incineration gives ash, flue gas, and heat as the final product. Three types of waste to which incineration is applied extensively are municipal solid waste, hazardous waste, and medical waste. Incineration of those three types is the focus of this discussion.

2. Autoclave: An autoclave is a machine that uses steam under pressure to kill harmful bacteria, viruses, fungi, and spores on items that are placed inside a pressure vessel.

• The items are heated to an appropriate sterilization temperature for a given amount of time.
• An autoclave is used to sterilize surgical equipment, laboratory instruments, pharmaceutical items, and other materials. It can sterilize solids, liquids, hollows, and instruments of various shapes and sizes.

3. Microwave irradiation: Microwave irradiation involves electromagnetic wave in the range of 300 MHz–300 GHz. Typical microwave ovens or microwave reactors work at a frequency of 2.45 GHz. Microwave irradiation produces efficient internal heating by direct coupling of microwave energy with the molecules of biomass.

4. Inertization: Inertization, or inerting, is an explosion protection process that uses inert gas to prevent the formation of an explosive mixture.

• Inerting systems are used to prevent: vapors from escaping into the atmosphere (contamination) and air from penetrating into the plant (oxidation). inert gases are non-combustible, non-flammable, and non-reactive to many materials.
• Examples include argon, helium, nitrogen, and neon. Some inert gases are also cryogenic in their liquid state.

5. Chemical Disinfection: Chemical disinfection consists of adding a disinfectant (generally a strong oxidant) to the water, which reacts with the organic matter and microbial organisms.

• The most frequent chemical disinfection compounds are chlorine dioxide, chlorine, and chloramines on one hand, and ozone on the other hand.
• These include alcohols, chlorine and chlorine compounds, formaldehyde, glutaraldehyde, ortho-phthalaldehyde, hydrogen peroxide, iodophors, peracetic acid, phenolics, and quaternary ammonium compounds.

6. Land Disposal Definition: The discharge, deposit, or injection of any waste onto or into the soil or other land surfaces.

• Landfills are sites designated for dumping rubbish, garbage, or other sorts of solid waste. Historically, they are the most common means of disposing of solid waste which is either buried or left to pile in heaps.
• Some landfills are well-managed and designed as part of integrated waste management.

“Role of personal protective equipment (PPE) in infection control: Questions answered”

Question 13. What is nosocomial infection? Describe various types of nosocomial infections in detail.
Answer:

Hospital-acquired infection (HAI)/nosocomial infection — is an infection that is contracted from the environment or staff of a healthcare facility.

• The term Nosocomial is taken from the Greek word Nosocomium meaning healthcare facility.
• It is also known as hospital-acquired infection.
• Nosocomial infection is one that is acquired in a hospital or health care agency.
• A hospital is one of the most likely places for acquiring an infection because it harbors high population of viral and strains of microorganisms that are usually resistant to do antibiotics.

Types of hospital Acquired Infection

1. Bloodstream infection: This includes bacteria and septicemia which are generally caused by the introduction of intravascular catheter cannulas.
2. Pneumonia -ventilator-associated pneumonia(VAP) in ICU patient patients with prior respiratory tract pathology smokers patients who have undergone abdominal of thoracic surgery are usually affected.
3. Urinary tract infection it is usually caused by the introduction of eggs in organisms’ urinary tract catheter for urinary tract instrumentation.
4. Gastrointestinal infection it can occur by the consumption of contaminated food and cause food poisoning manifested by vomiting diarrhea or dysentery.
5. Skin and soft tissue infection it can occur by surgical procedures contamination of wounds and secondary infection of traumatic wound Examples of positive microorganisms

Question 14. Define hospital-acquired infection. Write a note on hospital infection control committee or program.
Answer:

Hospital-acquired infection (HAI)/nosocomial infection — is an infection that is contracted from the environment or staff of a healthcare facility.

• The term Nosocomial is taken from the Greek word Nosocomium meaning healthcare
  facility.
• It is also known as hospital-acquired infection. Nosocomial infection is one that is acquired in hospital or health care agency.
• This committee bears the responsibility of infection control measures with an objective of reducing the risk of HAI in the hospital. The committee discusses and decides on each matter that can have an effect on infection control.

Hospital-acquired Infection Roles And Responsibilities

• Develop and approve organization-wide infection control programs, policies, activities, and manual
• Establish standard precaution practices to be followed across the hospital
• Establish definitions and criteria for identifying and reporting of all infections among patients and personnel
• Guide departments on evidence-based infection control practices
• Set benchmark HAI rates for monitoring the effectiveness of infection control measures
• Validate methods for calculating HAI rates
• Review HAI rates periodically and recommend actions accordingly
• Develop antibiotic policy in conjunction with the pharmaco-therapeutics committee
• Develop protocol for handling of infection outbreaks and manage such situations
• Other similar matters related to infection control

Suggested members

35/17 Chairperson – Someone from top management such as CEO, Vice president or director or Medical Superintendent.

35/17 Convener or Coordinator – Infection Control Officer or Medical Microbiologist or Infectious diseases specialist

35/17 Clinical members – One representative each from all clinical specialties and super-specialties, including Anesthesiology, Critical Care, Emergency Medicine, Laboratory services, Blood Bank, Nursing Services, and Allied health specialties

Non-clinical members – Person in charge for the administration of Operation theatre, ICU, IPD, OPD, Emergency department, CSSD, Laundry, Bio-medical waste, Maintenance, Medical Equipment, and General Management

Question 15. Write down the various sources and routes or modes of transmission of infection.
Answer:

Sources of Infection Endogenous:

• § Patients’ own flora may invade the patient’s tissue during some surgical operations or instrumental manipulations
• § Normal commensals of the skin, respiratory, GI, UG tract

Sources of Infection Exogenous:

• § From another patient or staff member or environment in the hospital
• § Environmental sources: Inanimate objects, air, water, food
• § Cross infection from other patients, hospital staff (suffering from infections or asymptomatic carriers)

Modes of Transmission Of Infection:

1. Contact: Most common route of transmission

• Hands of staff: important vehicle of spread. Contact of hands and clothing of attendants
  • Hands of staff Example: Staphylococcus aureus, Streptococcus pyrogens
• Inanimate objects: Improper disinfection of Instruments: endoscope, bronchoscope, cystoscope
  • Inanimate objects Example: Pseudomonas aeruginosa

2. Airborne:

Droplets: Droplets of Respiratory infections: transmitted by inhalation

Dust: Dust from bedding, floors, wound exudates, and skin. Example: Pseudomonas aeruginosa, Staphylococcus aureus

Aerosols: Aerosols from nebulizers, humidifiers, and AC. Example: Legionella pneumophila

3. Oral Route: Hospital food may contain Antibiotic-resistant bacteria → may colonize the intestine → can cause infections

4. Parenteral route:

• Disposable syringes and needles
• Certain infections may be transmitted by blood transfusion, tissue donation, or contaminated blood products.
  • Example: Hepatitis B, HIV

Question 16. Explain in detail the portals of entry and exit of microorganisms.
Answer:

Portals Of Entry (Entry Of Microbes Into Body): To cause any infection, pathogens must enter the body through certain pathways or routes called portals of entry which differ for various organisms.

Most of the pathogens can cause infection only if they enter through a particular route. The portals of entry may be:

1. Alimentary tract: This tract serves as a portal of entry of the pathogenes causing typhoid, dysentery, and cholera. These pathogens are taken to the alimentary tract via ingestion of contaminated milk, food, or water through the mouth.
2. Respiratory tract: This tract is a portal of entry of pathogens causing diphtheria, TB, pneumonia, etc. These pathogens have a special affinity for the respiratory tract and enter via
   inhalation or through the mucous membrane of the mouth, nose to throat, tonsils, and lungs.
3. Urogenital tract: Some pathogens enter the body by coming in contact with the urogenital tract and are an important cause of STDs. example: pathogens causing AIDS, gonorrhea, syphilis.
4. Inoculation: Some pathogens enter the body through the skin or mucous membrane through abrasions, wounds, or burns and cause severe wound infection. Example: spores of Cl.tetani enter the wound causing tetanus, Hep. B transmitted by transfusion of contaminated blood or inoculation of infected blood products.

Portals Of Exit (Exit Of Microbes From Body): The pathogens exit from the body of an infected person or carrier through certain routes or pathways called portals of exit.

The portals exist differ for different microorganisms depending upon the site or location of infection. The portal of exit may be:

• Feces
• Urine
• Sputum/saliva
• Skin and mucous membrane (secretion)
• Nose and throat secretions
• Eye secretions
• Blood

“How do standard precautions reduce infection risks? FAQ explained”

Question 17. What is asepsis? Write a detailed note on aseptic techniques.
Answer:

Asepsis Definition: Asepsis is the state of being free from disease-causing contaminants such as bacteria, viruses, fungi, and parasites or, preventing contact with microorganisms. There are two types of asepsis.

Medical asepsis, also known as the “clean technique” is aimed at controlling the number of microorganisms and is used for all clinical patient care activities. Surgical asepsis, also known as the “sterile technique” is aimed at removing all microorganisms and is used for all surgical/sterile procedures.

1. Medical asepsis: Medical asepsis is the state of being free from disease-causing microorganisms. Medical asepsis is concerned with eliminating the spread of microorganisms through facility practices. So cleaning up spills, and dirty surfaces and using disinfectant would be examples of this. Medical asepsis also includes the use of PPE (personal protective equipment), like gloves, gowns, and even masks, eye and face shields.

2. Surgical asepsis: Surgical asepsis is the absence of all microorganisms within any type of invasive procedure. The sterile technique is a set of specific practices and procedures performed to make equipment and areas free from all microorganisms and to maintain that sterility. The goal of asepsis is to prevent the contamination of the open surgical wound by isolating the operative site from the surrounding nonsterile environment.

Aseptic technique means using practices and procedures to prevent contamination from pathogens. It involves applying the strictest rules to minimize the risk of infection. Healthcare workers use the aseptic techniques in surgery rooms, clinics, outpatient care centers, and other health care settings.

Following aseptic technique helps prevent the spread of pathogens that cause infection.

• Healthcare professionals commonly use aseptic technique when they’re:
• Handling surgery equipment
• Helping with a baby’s birth by vaginal delivery
• Handling dialysis catheters
• Performing dialysis
• Inserting a chest tube
• Inserting a urinary catheter
• Inserting central intravenous (4) or arterial lines
• Inserting other draining devices
• Performing various surgical techniques

Aseptic technique benefits: Whenever your skin is opened, you’re vulnerable to infection. That’s why it’s critical for you to get prompt treatment for burns and wounds.

• Even intentional cuts during surgery put you at risk for infection. The way healthcare providers use aseptic techniques before, during, and after your procedure helps protect you from infection.
• When you need surgery or other procedures that require an aseptic technique, you’re already vulnerable to infections. You need your immune system to be at its strongest to heal. You have a better chance of recovery if you don’t have to fight off an infection.

Question 18. Write a note on biomedical waste and its management.
Answer:

Biomedical waste or hospital waste is any kind of waste containing infectious (or potentially infectious) materials. Waste sharps include potentially contaminated used (and unused discarded) needles, scalpels, lancets, and other devices capable of penetrating skin.

It may also include waste associated with the generation of biomedical waste that visually appears to be of medical or laboratory origin (for example, packaging, unused bandages, infusion kits, etc.), as well as research laboratory waste containing biomolecules or organisms that are mainly restricted from environmental release.

Biomedical waste is generated from biological and medical sources and activities, such as the diagnosis, prevention, or treatment of diseases. Common generators (or producers) of biomedical waste include hospitals, health clinics, nursing homes, emergency medical services, medical research laboratories, offices of physicians, dentists, veterinarians, home health care, and morgues or funeral homes. In healthcare facilities (i.e. hospitals, clinics, doctor’s offices, veterinary hospitals, and clinical laboratories), waste with these characteristics may alternatively be called medical or clinical waste.

Biomedical waste Management: Biomedical waste must be properly managed and disposed of to protect the environment, general public, and workers, especially healthcare and sanitation workers who are at risk of exposure to biomedical waste as an occupational hazard. Steps in the management of biomedical waste include generation, accumulation, handling, storage, treatment, transport, and disposal.

Accumulation, handling, and storage: Biomedical waste is generated from various sources. it is accumulated on those areas. So source identification is done on that site called segregation of the area. handling all waste carefully. And store for few hours till the transport vehicle comes to collect it.Store in a safe area.

Treatment, Disposal: The goals of biomedical waste treatment are to reduce or eliminate the waste’s hazards, and usually to make the waste unrecognizable. Treatment should render the waste safe for subsequent handling and disposal. There are several treatment methods that can accomplish these goals.

• It includes segregating the bio waste Biomedical waste is often incinerated. An efficient incinerator will destroy pathogens and sharps.
• Source materials are not recognizable in the resulting ash. Alternative thermal treatment can also include technologies such as gasification[8] and pyrolysis including energy recovery with similar waste volume reductions and pathogen destruction.
• An autoclave may also be used to treat biomedical waste. An autoclave uses steam and pressure to sterilize the waste or reduce its microbiological load to a level at which it may be safely disposed of.
• Many healthcare facilities routinely use an autoclave to sterilize medical supplies. If the same autoclave is used to sterilize supplies and treat biomedical waste, administrative controls must be used to prevent the waste operations from contaminating the supplies.
• Effective administrative controls include operator training, strict procedures, and separate times and space for processing biomedical waste. Microwave disinfection can also be employed for treatment of Biomedical wastes. Or By Volume reduction processess.

“Early warning signs of gaps in understanding infection control basics: Common questions”

Question 19. Sources of infection
Answer:

Infection and immunity involve interaction between the animal body (host) and the infecting microorganisms. The lodgement and multiplication of a parasite in or on the tissues of a host constitute infection. It does not invariably result in disease.

Sources Of Infection

1. Human beings
2. Animals
3. Insects
4. Soil and water
5. Food.

1. Human Beings: The most common source of infection for human beings is human beings themselves. The parasite may originate from a patient or carrier.

Humans serving as the microbial reservoir:

1. Acquisition of “strep” throat through touching
2. Hepatitis by blood transfusions
3. Gonorrhea, syphilis, and AIDS by sexual contact
4. Tuberculosis by coughing; and the common cold through sneezing.

2. Animals: Reservoir hosts: Many pathogens are capable of causing infections in both human beings and animals. Therefore, animals may act as a source of infection of such organisms. These animals serve to maintain the parasite in nature and act as reservoir and they are, therefore, called reservoir hosts.

Zoonosis: The diseases and infections, which are transmissible to man from animals are called zoonosis.

Examples of zoonotic diseases

Bacterial: Anthrax, brucellosis, Question fever, leptospirosis, bovine tuberculosis, bubonic plague, Salmonella food poisoning.

Viral: Rabies, yellow fever, cowpox, monkeypox.

Protozoal: Leishmaniasis, toxoplasmosis, trypanosomiasis, babesiosis.

Helminthic: Echinococcosis, taeniasis, trichinellosis.

Fungal: Microsporum canis, Trichophyton verrucosum.

3. Insect – Arthropod-Borne Diseases: Blood-sucking insects, such as mosquitos, ticks, mites, ies, and lice may transmit pathogens to human beings, and diseases so caused are called arthropod-borne diseases.

Insect – Arthropod-Borne Diseases Vectors: Insects that transmit infections are called vectors. Vector-borne transmission can be of two types either mechanical (external) or biological (internal).

1. Mechanical vector: The disease agent is transmitted mechanically by the arthropod.
   • Mechanical vector Examples: Transmission of diarrhea, dysentery, typhoid, food poisoning, and tracghoma by the house.
2. Biological vectors: Biological vectors are those in whom the pathogens multiply succinctly or has undergone a developmental cycle. The interval between the time of entry of the pathogen into the vector and the vector becoming infective is called the extrinsic incubation period.
   • Biological vectors Examples: Aedes aegypti mosquito in yellow fever, Anopheles mosquito in malaria.
   • Reservoir hosts: Besides acting as vectors, some insects may also act as reservoir hosts (for example, ticks in relapsing fever and spotted fever). Infection is maintained in such insects by transovarial or transstadial passage.

4. Soil And Water

Soil: Some pathogens can survive in the soil for long periods.

Soil Examples

• Spores of tetanus and gas gangrene: Spores of tetanus and gas gangrene remain viable in the soil for several decades and serve as source of infection.
• Fungi and parasites: Fungi (causing mycetoma, sporotrichosis, histoplasmosis) and parasites such as roundworms and hookworms also survive in the soil and cause human infection.

Water: Water may act as the source of infection either due to contamination with pathogenic microorganisms (Shigella, Salmonella, Vibrio cholerae, poliomyelitis virus, hepatitis virus) or due the presence of aquatic vector (cyclops containing larvae of guinea worm infection).

5. Food: Contaminated food may act as source of infection of organisms causing food poisoning, gastroenteritits, diarrhea and dysentery.

“Asymptomatic vs symptomatic effects of ignoring infection control practices: Q&A”

Question 20. Classification of infection
Answer:

The lodgement and multiplication of a parasite in or on the tissues of a host constitute infection. It does not invariably result in disease.

Classification Of Infections: Infections may be classied in various ways

1. Primary infection: Initial infection with a parasite in a host is termed primary infection.
2. Reinfections: Subsequent infections by the same parasite in the host are termed reinfections.
3. Secondary infection: When a new parasite sets up an infection in a host whose resistance is lowered by a preexisting infectious disease, this is termed secondary infection.
4. Local infection: The term local infection (more appropriately local sepsis) indicates a condition where, due to infection or sepsis at localized sites such as appendix or tonsils, generalized effects are produced.
5. Cross-infection: When in a patient already suffering from a disease, a new infection is set up from another host or another external source, it is termed cross-infection.
6. Nosocomial infections: Cross-infections occurring in hospitals are called nosocomial infections (from Greek nosocomion hospital).
7. Iatrogenic infection: The term iatrogenic infection refers to physician induced infections resulting from investigative, therapeutic or other procedures.
8. In apparent infection: In apparent infection is one where clinical effects are not apparent.
9. Subclinical infection: The term subclinical infection is often used as a synonym to in apparent infection.
10. Atypical infection: Atypical infection is one in which the typical or characteristic clinical manifestations of the particular infectious disease are not present.
11. Acute infection: An infection which lasts for a relatively short time. (few days to few weeks). Example: Measles.
12. Chronic infection: An infection which lasts for a long time (over months and years). Example: TB.
13. Autoinfection: An infection that occurs between two sites on the same host.(worms)
14. Mixed infection: An infection caused by two or more organism.(bacterial vaginosis)
15. Masked infection: An infection is known to occur but the infectious agent cannot be demonstrated.
16. Oppurtunistic infection: An infection with organisms which are normally harmless but become pathogenic when the body’s defence mechanisms are compromised.

“Steps to incorporate AI into analyzing infection control practices: Questions and answers”

Question 21. Define carrier and its classification with examples.
Answer:

1. Carrier: A carrier is person who harbours or lodge of the microorganisms without suffering from any ill effect’ because of it. There are several types of carriers
2. Convalescent carrier: An individual who has recovered from the infectious disease but continues to harbour or lodge large numbers of pathogen.
3. Healthy carrier: A healthy carrier is an individual who harbours or lodge the pathogen but is not ill.
4. Incubatory carrier: An incubatory carrier is an individual who is incubating the pathogen in large numbers but is not yet ill.
5. Temporary carriers: Convalescent, healthy, and incubatory carriers may harbour or lodge the pathogen for only a brief period (hours, days, or weeks) and lasts less than six months.
6. Chronic carriers: They harbour the pathogen for long periods (months, years, or life).
7. Contact carriers: The term contact carrier is applied to a person who acquires the pathogen from a patient.
8. Paradoxical carrier: This refers to a carrier who acquires the pathogens from another carrier.

The post BSc Nursing 1st Year Microbiology Nursing Chapter 3 Infection Control Question And Answers appeared first on BDS Notes.

Question 1. Draw a neat labelled diagram of a Bacterial cell.
Answer:

Question 2. Differentiate between Gram-positive bacteria and Gram-negative bacteria
Answer:

“Understanding general characteristics of microbes through FAQs: Q&A explained”

Question 3. Differentiate between Flagella and Fimbriae.
Answer:

Question 4. Differentiate between Prokaryotic and eukaryotic cell.
Answer:

“Importance of studying microbes for BSc Nursing students: Questions explained”

Prokaryotic And Eukaryotic Cell Example:

• Fungi, protozoa, plants, animals
• Eubacteria, All bacteria, and blue-green algae

Question 5. Bacterial Growth curve.
Answer:

Bacterial Growth Curve:

• If a suitable liquid medium is inoculated with bacterium and incubated, its growth follows a definitive course.
• Small samples are taken at regular intervals after inoculation and plotted in relation to time. A plotting of the data will yield a characteristic growth curve.
• The changes of slope on such a graph indicate the transition from one phase of development to another.

Phases of Bacterial Growth Curve: The bacterial growth curve can be divided into four major phases:

1. Lag phase
2. Exponential or log (logarithmic) phase
3. Stationary phase, and
4. Decline phase.

These phases reflect the physiologic state of the organisms in the culture at that particular time.

1. Lag Phase: After inoculation of the culture medium, multiplication usually does not begin immediately.
   • The period between inoculation and beginning of multiplication is known as lag phase.
   • During this period the organisms adapt to the new environment, during which necessary enzymes and intermediate metabolites are built up in adequate quantities for multiplication to proceed.
   • There is an increase in the size of the cells but there is no appreciable increase in numbers.
2. Log (Logarithmic) or Exponential Phase: The cell division starts and their numbers exponentially or by geometric progression with time. If the logarithm of the viable count is plotted against time, a straight line is obtained.
3. Stationary Phase: After the log phase, bacterial growth ceases almost completely due to exhaustion of nutrients and accumulation of toxic products. The number of progeny cells formed is just enough to replace the number of cells that die. The number of viable cells remains stationary as there is almost a balance between the dying cells and the new formed cells.
4. The phase of Decline: Alter a period of stationary phase, the bacterial population decreases due to the death of cells. The decline phase starts due to the exclusion of nutrients, accumulation of toxic produce, and autolytic enzymes. There is decline in viable count and not in total count.

Read And Learn More: Bsc Nursing 1st Year Microbiology Previous year Question and Answers

“Common challenges in understanding characteristics of microbes effectively: FAQs provided”

Question 6. Gram Staining.
Answer:

The technique was developed by a Danish physician. Dr hanes Cristain Gram 1884. This is a useful differential staining procedure in bacteriology which besides determining gross morphology differentiates

Bacteria into two major distinct groups:

1. Gram Positive
2. Gram Negative

The technique involves six basic steps:

1. Smear preparation
2. Heat fixing of smear
3. Staining with a crystal violet (Primary staining)
4. Use of iodine.
5. Treatment with acetone alcohol mixture (Decolourizing agent).
6. Use of safarin (Colour stain).

Gram Staining Principale: The peculiar response toward the staining is related to physical and chemical differences in the cell wall of the two groups of bacteria.

• In gram-negative bacteria the cell wall is thin and multilayered containing high lipid contents that are readily dissolved by alcohol, resulting in pore formation in the cell wall facilitating the leakage of the crystal violet iodine complex of resulting in discoloration of gram-negative
  bacteria which takes safarin and appears red.
• On the other hand. Cell walls of gram-positive bacteria are thick, composed mainly of proteins and crossed-linked mucopeptides on the application of a decolorizing agent, dehydration results in closure of pores of cell wall thereby retaining the CV-1 complex and appearing blue or Purple.

“Why is early learning of microbial characteristics critical for nursing practice? Answered”

Gram Staining Reagents Used:

1. Crystal violet
2. Gram iodine solution
3. Ethyl alcohol (15%) or Alcohol acetone (1:1) solution.
4. Safranin Solution

Gram Staining Procedure:

1. Make smear of a given culture on a clear glass slide.
2. Air dry the smear and heat fix it.
3. Cover the smear completely with crystal violet stain and leave the stain on the slide for one minute.
4. Wash the slide gently in distilled water or tap water
5. Flood the spray with gram iodine solution for 1 minute.
6. Wash with tap water gently and drain carefully.
7. Wash the slide gently under running water for 30 min.
8. Now counter-stain with Safari and wait for 30 min
9. Wash again and flot dry with bloting paper or simply air dry the slide and observe under oil. Immersion objective.

Gram Staining Result:

1. Bacteria that appear blue / violet/purple are assigned as gram-positive.
2. While those appearning red/pink are assigned as gram negative.

Question 7. Acid-fast staining.
Answer:

• The technique was developed by Paul Ehrlich. and was modified later by Ziehl Nelson.
• This is a differential staining used to identify mainly the members of mycobacterium, especially these organisms are difficult to stain by ordinary staining method due to the presence of high lipid content in their cell walls.

Bacteria are Classified as:

1. Acid-fast: They retain primary stain after the application of strong the application of strong acid and appear red
2. Non-acid fast: if they not retain the primary stain and are counter-stained by methylene blue.

Acid Fast Staining Reagent:

1. Carbol fusion solution.
2. Acid alchol solution (20 – 25 % v/v in water)
3. Methylene blue counter stain (0.3 w/v aqueous)

Acid Fast Staining Procedure:

1. Prepare a smear of purulent portion of the specimen on a clean glass slide
2. Air dry and heat fix the smear
3. Flood the smear with freshly filtered carbol Fuchisin. Heat gently until steam rises.
4. Cool and wash the stain of the slide with H₂O
5. Cover the slide with an acid alcohol solution for 3 min. Wash with running tap water and drain Finally, wash it.
6. Cover the slide with methylene blue stain and leave it for 2 min.
7. Wash with tap water, blot dry or air dry the slide, and observe under an oil immersion object.

Acid Fast Staining Result: Acid-fast organisms will appear bright red on a blue background. While as nonacid fast organisms will appear dark blue in colour.

“Steps to explain the structure of microbes: Prokaryotes vs eukaryotes: Q&A guide”

Question 8. Hanging drop method.
Answer:

Hanging drop preparation is a special type of wet mount (in which a drop of medium containing the organisms is placed on a microscope slide), often is used in dark illumination to observe the motility of bacteria.

Hanging Drop Method Preparation

• In this method, a drop of culture is placed on a coverslip that is encircled with petroleum jelly (or any other sticky material).
• The coverslip and drop are then inverted over the well of a depression slide. The drop hangs from the coverslip, and the petroleum jelly forms a seal that prevents evaporation. This preparation gives good views of microbial motility.

Hanging Drop Method Materials Required

1. Glass slides (glass slide with depression) or normal glass slide with adhesive or paraffin ring
2. Paraffin wax
3. Loop
4. Coverslip
5. Microscope
6. Bunsen burner
7. Young broth culture of motile bacteria (for example, Proteus mirabilis)

Hanging Drop Method Procedure

1. Take a clean glass slide and apply a paraffin ring, and adhesive tape ring to make circular concavity. (This step is not needed if a glass slide with depression is available).
2. Hold a clean coverslip by its edges and carefully dab Vaseline on its corners using a toothpick.
3. Place a loopful of the broth culture to be tested in the center of the prepared coverslip.
4. Turn the prepared glass slide or concavity slide upside down (concavity down) over the drop on the coverslip so that Vaseline seals the coverslip to the slide around the concavity.
5. Turn the slide over so the coverslip is on top and the drop can be observed hanging from the coverslip over the concavity.
6. Place the preparation in the microscope slide holder and align it using the naked eye so an edge of the drop is under the low power objectives.
7. Turn the objective to its lowest position using the coarse adjustment and Close The Diaphragm.
8. Look through the eyepiece and raise the objective slowly using the coarse adjustment knob until the edge of the drop is observed as an irregular line crossing the field.
9. Move the slide to make that line (the edge of the drop) pass through the centre of the field.
10. Without raising or lowering the tube, swing the high dry objective into position (Be sure the high dry objective is clean).
11. Observe the slide through the eyepiece and adjust the fine adjustment until the edge of the drop can be seen as a thick, usually dark line.
12. Focus the edge of the drop carefully and look at each side of that line for very small objects that are bacteria. The cells will look either like dark or slightly greenish, very small rods or spheres. Remember the high dry objective magnifies a little less than half as much as the oil immersion objective.
13. Adjust the light using the diaphragm lever to maximize the visibility of the cells.
14. Observe the cells noting their morphology and grouping and determine whether true motility can be observed.
15. Brownian movement should be visible on slides of all the organisms, but there should also show true motility.
16. Wash the depression slide and after soaking in lysol buckets or discard the prepared glass slide.

“Role of microbial morphology in identification: Questions answered”

Hanging drop slides are useful in observing the general shape of living bacteria and the arrangement of bacterial cells when they associate together. Organisms are observed in a drop that is suspended under a cover glass in a concave depression slide.

Question 9. Bacterial flagella.
Answer:

Bacterial Flagella: Motile bacteria, except spirochetes, possess one or more unbranched, long, sinuous filaments called flagella, which are the organs of locomotion.

Bacterial Flagella Structure: They are long, hollow, helical filaments, usually several times the length of the cell. They are 3-20 µm long and are of uniform diameter (0.01-0.013 µm) and terminate in a square tip. Flagella can be found on both gram-positive and gram-negative bacilli.

Flagella Parts and Composition: Each flagellum consists of three parts

1. Filament
2. Hook
3. Basal body.

“How do size and shape define microbial behavior? FAQ explained”

1. Filament: The filament is the longest and most Obvious portion which extends from the cell surface to the tip.
2. Hook: The hook is a short, curved segment that links the filament to its basal body and functions as the universal joint between the basal body and the filament.
3. Basal body: The basal body is embedded in the cell (cytoplasmic membrane). In gram-negative bacteria, the basal body has four rings connected to a central rod (L, P, S, and M).

Gram-positive bacteria have only two basal body rings, an inner ring connected to the cytoplasmic membrane and an outer one probably attached to peptidoglycan.

Flagella Arrangement Or Types:

• The number and location of flagella are distinctive for each genus. There are four types of flagella arrangement:
• Monotrichous—Single polar flagellum (example, Cholera vibrio).
• Amphitrichous—Single flagellum at both ends (example, Alcaligenes faecalis). Types of flagella arrangement
• Lophotrichous—Tuft of flagella at one or both ends (example, spirilla).
• Peritrichous—Flagella surrounding the cell (for example, Typhoid bacilli).
• Flagella are about 0.02 µm in thickness and hence beyond the resolution limit of the light microscope.

“Early warning signs of gaps in understanding microbial basics: Common questions”

Question 10. Bacterial Spore
Answer:

Bacterial Spore

• A number of gram-positive bacteria, such as those of the genera Clostridium and Bacillus can form a special resistant dormant structure called an endospore or, simply, spores.
• Endospores develop when essential nutrients are depleted. In sporulation, each vegetative cell forms only one spore, and in subsequent germination, each spore gives rise to a single vegetative cell.
• Sporulation in bacteria, therefore, is not a method of reproduction but of preservation.

Bacterial Sporulation: Spore formation, sporogenesis or sporulation normally commences when growth ceases due to lack of nutrients, depletion of the nitrogen or carbon source (or both) being the most significant factor. New antigens appear on sporulation that are not found in the vegetative cell.

Bacterial Spore Stages: It is a complex process and may be divided into several stages.

1. Bacteria Spore septum: In the first observable stage of sporulation, a newly replicated bacterial chromosome and a small portion of cytoplasm are isolated by an ingrowth of the plasma membrane called a spore septum.
2. Forespore: The spore septum becomes a double-layered membrane that surrounds the chromosome and cytoplasm. Structure, entirely enclosed within the original cell, is called a forespore.
3. Spore coat: The forespore is subsequently completely encircled by dividing septum as a double-layered membrane. The two spore membranes now engage in active synthesis of various layers of the spore. The inner layer becomes the inner membrane. Between the two layers is laid spore cortex and outer layer is transformed into a spore coat which consists of several layers. In some species from outer layer also develops exosporium which bears ridges and folds.
4. Free endospore: Finally exosporium disintegrates and the endospore is freed.

“Asymptomatic vs symptomatic effects of ignoring microbial characteristics: Q&A”

Question 11. Explain in detail about morphology of bacteria and structural components of bacterial cell along with their function.
Answer:

• Bacteria are very small in size. The unit of measurement in bacteriology is the micron or micrometer (mm).
• Bacteria of medical importance generally measure 0.2-1.5 µm in diameter and about 3-5 µm in length. To see bacteria, a light microscope must be used.

Shape of Bacteria Depending on their shape, bacteria are classified into several varieties:

1. Cocci: Cocci (from kokkos meaning berry) are spherical, or nearly spherical.
2. Bacilli: Bacilli (from bacillus meaning rod) are relatively straight, rod-shaped (cylindrical) cells. In some of the bacilli, the length of the cells may be equal to width. Such bacillary forms are known as lactobacilli and have to be carefully differentiated from cocci.
3. Vibrios: Vibrios are curved or comma-shaped rods and derive their name from their characteristic vibratory motility.
4. Spirilla: Spirillas are rigid spiral or helical forms.
5. Spirochetes: Spirochetes (from spiral meaning coil and chaite meaning hair) are flexuous spiral forms.
6. Mycoplasma: Mycoplasma are cell wall deficient bacteria and hence do not possess a stable morphology. They occur as round or oval bodies and interlacing filaments.

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Cocci Arrangement

1. Diplococci: Cocci may be arranged in pairs (diplococci) when cocci divide and remain together.
2. Long chains: Long chains (Streptococcus, Enterococcus, and Lactococcus) when cells adhere after repeated divisions in one plane.
3. Grape-like clusters: Grape-like clusters (staphylococci) when cocci divide in random planes.
4. Tetrads: Square groups of four cells (tetrads) when cocci divide in two planes as in members of the genus Micrococcus.
5. Cubical packets: Cubical packets of eight of cells (genus Sarcina) when cocci divide in three planes.

Structural components of bacterial cell: Bacterial Cell Components can be divided into

The outer layer or cell envelope consists of two components:

1. Cell wall.
2. Cytoplasmic or plasma membrane—beneath cell wall.

Cellular appendages—Besides these essential components, some bacteria may possess additional structures such as capsules, fimbriae, and flagella.

Capsule: Some bacteria produce a protective gelatinous covering layer called a capsule outside the cell wall. If the capsule is too thin to be seen with light microscope (<0.2 µm) it is called a microcapsule.

Loose slime: Soluble, large-molecular, amorphous, viscid colloidal material may be dispersed by the bacterium into the environment as loose slime.

Flagella: Some bacteria carry external filamentous appendages protruding from the cell wall flagella, which are organs of locomotion fimbriae, which appear to be organs of adhesion and pili, which are involved in the transfer of genetic material.

The Outer Layer or Cell Envelope

1. Cell Wall: The cell wall is the layer that lies just outside the plasma membrane. It is 10-25 nm thick, strong, and relatively rigid, though with some elasticity, and openly porous, being freely permeable to solute molecules smaller than 10 kDa in mass and 1 nm in diameter.

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Functions of the cell wall:

1. To impart shape and rigidity to the cell.
2. It supports the weak cytoplasmic membrane against the high internal osmotic pressure of the protoplasm (ranges from 5 and 25 atm).
3. Maintains the characteristic shape of the bacterium.
4. It takes part in cell division.
5. Also functions in interactions (for example, adhesion) with other bacteria and with mammalian cells.
6. Provide specific protein and carbohydrate receptors for the attachment of some bacterial viruses.

Chemical Structure of Bacterial Cell Wall: Chemically the cell wall is composed of mucopeptide (peptidoglycan or murein) scaffolding formed by N-acetyl glucosamine and N-acetyl muramic acid molecules alternating in chains, which are crosslinked by peptide bonds. Peptidoglycan consists of three parts

1. A backbone— composed of alternating N-acetylglucosamine and N-acetylmuramic acid.
2. A set of identical tetrapeptide side chains attached to N-acetylmuramic acid.
3. A set of identical pentapeptide cross-bridges

“Steps to apply microbial characteristics in clinical practice: Identification vs diagnosis: Q&A guide”

Question 12. Define culture media and classify them on the basis of various methods in detail.
Answer:

Culture Medium Introduction: A nutrient material prepared for the growth of microorganisms in a laboratory is called a culture medium.

Classification Of Culture Media: Media have been classified into many ways

1. Phases Of Growth Media: Growth media are used in either of the two phases.

1. Liquid (Broth) Media: In broth media, nutrients are dissolved in water, and bacterial growth is indicated by a change in broth’s appearance from clear to turbid (i.e. cloudy).
2. Solid (Agar) Media: Solid media are made by adding a solidifying agent to the nutrients and water. Agarose is the most common solidifying agent. The Petri dish containing the agar is referred to as agar.
3. Semisolid Media: For special purposes where agar is added to media in concentrations that are too low to solidify them.

2. Based On Nutritional Factors

1. Simple media (Basal media): Simple media are those which contain only basic nutrients required for the growth of ordinary organisms, and are used as a general-purpose media, for example, peptone water, nutrient broth, and nutrient agar.
2. Complex media: Media that contain some ingredients of unknown chemical composition are called complex media. One common ingredient is peptone. Extracts, which are the water-soluble components of a substance, are also used.
3. Synthetic Or Chemically Defined Media: They are prepared exclusively from pure chemical substances and their exact composition is known.

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3. Special Media

1. Enriched Media: These are prepared to meet the nutritional requirements of more exacting bacteria by the addition of substances such as blood, serum, or egg to a basal medium.
   • Examples Of Enriched Media
     1. Blood agar
     2. Chocolate agar
2. Selective Media: When a substance is added to a solid medium that inhibits the growth of unwanted bacteria but favors the growth of wanted bacteria, it is known as selective media. These media are used to isolate particular bacteria from specimens where mixed bacterial flora is expected.
   • Examples of selective media:
     1. Deoxycholate citrate agar (DCA): The addition of deoxycholate acts as a selective agent for dysentery bacilli (isolation of Shigellae).
     2. Lowenstein-Jensen medium: This medium is used for Mycobacterium tuberculosis.
     3. Bile salt agar (BSA): Bile salt is a selective agent. It farceurs the growth of only Vibrio cholerae and inhibits the growth of intestinal organisms.
3. Indicator Media: These media contain an indicator that changes colour when a bacterium grows in them.
   • Indicator Media Examples:
     • Wilson and Blair medium:
     • MacConkey agar
4. Differential Media: A medium, that has substances incorporated in it, enabling it to bring out differing characteristics of bacteria and thus helping to distinguish between them, is called a differential medium.
   • Differential Media Example:
     • MacConkey agar: MacConkey agar is both differential and selective.
5. Sugar Media: For the identification of most of the organisms, sugar fermentation reactions are carried out. Carbohydrate fermentation is used ‘for the characterization and identification of bacteria, particularly important in the study of Gram-negative bacilli. Sugar media are used to test fermentation.
   • Sugar used for sugar media: The term ‘sugar’ in microbiology denotes any fermentable
     substance. Glucose, lactose, sucrose, and mannitol are routinely employed for fermentation tests.
6. Transport Media: A transport medium is a holding medium designed to preserve the viability of microorganisms in the specimen but not allow multiplication.
   • Transport Media Examples
     • Stuart’s transport medium and Amines transport medium for gonococci.
     • Buffered glycerol saline for enteric bacilli.

“Role of microbial traits in disease prevention: Questions answered”

Question 13. Define and Draw a neat labelled diagram of bacterial spore.
Answer:

• Bacterial spores serve largely as a resting, or dormant, stage in the bacterial life cycle, helping to preserve the bacterium through periods of unfavorable conditions.
• Spore production is particularly common among Bacillus and Clostridium bacteria, several species of which are disease-causing.

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Question 1. Define the term microbiology.
Answer:

Microbiology is the study of living organisms of microscopic size.

Or

Microbiology is the branch of science that is concerned primarily with the biology of microorganisms and their effects on other living organisms. “Father of Microbiology”. The contributions of Louis Pasteur in Microbiology are very important.

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Question 2.Contributions of Louis Pasteur in Microbiology.
Answer:

Father of microbiology—Louis Pasteur is known as “Father of microbiology” because his contribution led to the development of microbiology as a separate scientific discipline.

Contributions of Louis Pasteur in Microbiology:

1. Coined the term Microbiology: Pasteur coined the term microbiology for the study of living organisms of microscopic size.
2. Proposed germ theory of disease: He established that putrefaction and fermentation was the result of microbial activity and that different types of fermentations were associated with different types of microorganisms.
3. Disapproved theory of spontaneous generation: He disapproved of the theory of spontaneous generation. In a series of classic experiments, Pasteur proved conclusively that all forms of life, even microbes, arose only from their like and not de novo.
4. Developed sterilization techniques: He introduced sterilization techniques and developed the steam sterilizer, hot-air oven, and autoclave in the course of these studies.
5. Developed methods and techniques for the cultivation of microorganisms
6. Studies on pebrine (silkworm disease), anthrax, chicken cholera, and hydrophobia.
7. Pasteurization: He devised the process of destroying bacteria, known as pasteurization (1863-65). This process (pasteurization) is employed to preserve milk and certain other perishable foods throughout the civilized world today.
8. Coined the term vaccine: It was Pasteur who coined the term vaccine for such prophylactic preparations to commemorate the first of such preparations namely cowpox, employed by Jenner for protection against smallpox.
9. Discovery of the process of attenuation and chicken cholera vaccine: An accidental observation that chicken cholera bacillus cultures left on the bench for several weeks lost their pathogenic, property but retained their ability to protect the birds against subsequent infection by them, led to the discovery of the process of attenuation and the development of live vaccines.
10. Developed live attenuated anthrax vaccine.
11. Developed rabies vaccine.
12. Noticed Pneumococci—Pneumococci were first noticed by Pasteur and Sternberg independently in 1881.

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Question 3. Koch postulates or principles of microbiology.
Answer:

Koch’s postulates: Koch’s postulates are a series of guidelines for the experimental study of infectious disease. According to these, a microorganism can be accepted as the causative agent of an infectious disease only if the following conditions are satisfied:

• Postulate 1: The organism should be regularly found in the lesions of the disease.
• Postulate 2: It should be possible to isolate the organism in pure culture from the lesions.

Read And Learn More: Bsc Nursing 1st Year Microbiology Previous year Question and Answers

• Postulate 3: Inoculation of the pure culture into suitable laboratory animals should reproduce the lesion of the disease.
• Postulate 4: It should be possible to reisolate the organism in pure culture from the lesions produced in the experimental animals.

Subsequently, an additional fifth criterion introduced states that specific antibodies to the organism should be demonstrable in the serum of patients suffering from the disease.

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Question 4. Explain in detail about Historical perspectives.
Answer:

Microbiology is the study of living organisms of microscopic size. Microbiology is divided in four eras the are as follows.

1. Discovery Era:
   • “Spontaneous generation” Aristotle (384-322) and others believed that living organisms could develop from non-living materials. In 13th century, Rogen Bacon described that the disease was caused by a minute “seed” or “germ”.
   • Antony Van Leeuwenhoek (1632 – 1723) Descriptions of Protozoa, basic types of bacteria, yeasts and algae. Father of Bacteriology and protozoology. In 1676, he observed and described microorganisms such as bacteria and protozoa as “Animalcules”.
2. Transition Era:
   • Francesco Redi (1626 – 1697) . He showed that maggots would not arise from decaying meat,
     when it is covered.
   • John Needham (1713 – 1781) Supporter of the spontaneous generation theory. He proposed that tiny organisms (animalcules) arose spontaneously on the mutton gravy. He covered the flasks
     with cork as done by Redi, Still, the microbes appeared on mutton broth.
   • Lazzaro spallanzai (1729 – 1799) . He demonstrated that air carried germs to the culture
     medium. He showed that boiled broth would not give rise to microscopic forms of life
3. Golden Era:
   • Louis Pasteur: He is the father of Medical Microbiology. He pointed that no growth took place in swan neck-shaped tubes because dust and germs had been trapped on the walls of the curved necks but if the necks were broken off so that dust fell directly down into the flask, microbial growth commenced immediately.
   • Robert Koch (1893-1910): He demonstrated the role of bacteria in causing disease.
   • Edward Jenner (1749-1823): First to prevent smallpox. He discovered the technique of vaccination.
   • Alexander Flemming: He discovered the penicillin from penicillium notatum that destroys several pathogenic bacteria.
4. Modern Era: Modern microbiology. Modern microbiology reaches into many fields of human endeavor, including the development of pharmaceutical products, the use of quality control methods in food and dairy product production, the control of disease-causing microorganisms in consumable waters, and the industrial applications of microorganisms.

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Question 5. Explain the germ theory of disease.
Answer:

1. The germ theory of disease postulated by Pasteur was later further developed by later scientists, such as Robert Koch.
2. The germ theory of disease is the currently accepted scientific theory for many diseases.
3. It states that microorganisms known as pathogens or “germs” can lead to disease.
4. These small organisms, too small to see without magnification, invade humans, other
   animals, and other living hosts.
5. Their growth and reproduction within their hosts can cause disease.
6. “Germ” may refer to not just a bacterium but to any type of microorganism or even nonliving pathogens that can cause disease, such as protists, fungi, viruses, prions, or viroids.
7. Diseases caused by pathogens are called infectious diseases.
8. Even when a pathogen is the principal cause of a disease, environmental and hereditary factors often influence the severity of the disease, and whether a potential host individual becomes infected when exposed to the pathogen.
9. The germ theory of disease postulated by Pasteur was later further developed by later scientists, such as Robert Koch

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