Normal Microbial Flora Of Human Body
Question 1. Write a short note on the microflora.
Answer:
A variety of microorganisms is normally present inside and outside of our body. The population of microorganisms which is normally present is known as microflora or normal microflora.
Normal microflora consists of saprophytes, commensals, facultative pathogens, and true pathogens. Most microorganism is normally present as commensals that exist in a symbiotic relationship with the host and obtain their nutrients from secretions as well as waste products of the body.
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Types of Microflora
Normal microbial flora is divided into two groups, i.e. resident Flora and transient flora.
- Resident Flora: It is also known as constant flora. It is composed of organisms that are regularly present in particular areas and when disturbed, they re-establish themselves, for example of most common example is E. coli which is the inhabitant of the small intestine.
- Benefits of Resident Flora:
- Resident flora prevents the colonization of the body by pathogens.
- Bacterial flora of the intestinal tract synthesizes vitamins, mainly vitamin K and several B vitamins.
- Production of antibodies in response to commensals cross-react with pathogens that share antigens and raise the overall immune status of the host against the pathogens.
- Colic ins which are produced by some of the organisms of normal flora produce harmful effects on pathogens.
- The liberation of endotoxins by normal microbial flora helps the defense mechanism of the body by triggering an alternate complement pathway.
- Production of Disease by Resident Flora:
- These bacteria become pathogenic when there is a decrease in host resistance
- These bacteria can act as pathogens in tissue away from their normal habitat.
- Normal microbial flora can lead to confusion in diagnosis because of their presence in the body and their resemblance to some pathogens.
- Transient Flora:
- It is also known as variable flora.
- It consists of non-pathogenic and potentially pathogenic bacteria which inhabit the body surface and mucus membrane for a limited period of time.
- These are eliminated from the body surface by mechanical means.
- An example is Pneumococcus and Meningococcus can be found in the nasopharynx of humans from time to time.
Question 2. Mention the names of bacteria producing infection in the oral cavity.
Answer:
Among all the microorganisms, bacteria are the most prominent to produce oral infection.
Bacteria Producing Oral Infection:
- Streptococci are the prominent group: Streptococcus mutans,
- S. Salivaris: The most important bacteria to cause dental caries.
- Lactobacillus: It is the most important bacteria to promote the progress of carious lesions.
- Bacteroides fragilis, S. sanguis, S. aureus, and Eikenella corrodens: These are the most common bacterias which lead to root canal infection and periapical infections.
- Oral treponemas (T. Denticle, T. orale): They have an important role in causing gingivitis and periodontitis.
- Staphylococcus aureus: It leads to parotitis.
Question 3. Write a short note on the normal flora of the mouth.
Or
Write a short answer on oral microbial flora.
Answer:
The normal oral cavity contains a mixture of organisms which includes bacteria, fungi, protozoa, and occasionally viruses.
- Some of the organisms are almost always present in a normal oral cavity and are called resident flora.
- Some organisms stay for a limited period in the oral cavity of a few individuals called transient flora.
- Among all the microorganisms present in the mouth, bacteria are the most predominant, these include both aerobic and anaerobic bacteria.
- Of all the bacteria present in the mouth, peptostreptococci are the predominant group.
- Most of these are alpha-hemolytic streptococci, collectively named as viridian streptococci.
- Streptococci mutants have been implicated as the most important bacteria to initiate dental caries.
- Lactobacilli are frequently found in the mouth they are important bacteria to promote the progress of carious lesions, often the initiation of dental caries.
- Veillonellae spp. Are the most numerous among gram-negative bacteria present in the oral cavity.
- Anaerobic gram-negative bacilli such as Bacteroides, Fusobacterium, Leptorichia, and Selenomonas have also been found.
- Fusobacterium nucleatum is the most commonly occurring gram-negative anaerobic bacillus in the gingival crevices and subgingival plaques.
- Oral treponemas are commonly found in gingival crevices and subgingival areas. Due to their presence, subgingival plaques, they have an important role in causing gingival diseases and most forms of periodontitis.
- Various other bacterial normal flora present in the mouth are Neisseria spp., Micrococci, Bacillus spp., coliform bacteria, Proteus spp., Mycoplasma spp., Corynebacterium spp., and non-pathogenic spirochaetes.
- Viruses are rarely encountered in mouth.
- Candida albicans is the most common fungus isolated from the mouth.
- Protozoans are also seen in some oral lesions.
Question 4. Write a short note on the normal flora of the upper and lower respiratory tract.
Answer:
Normal Flora of upper and lower Respiratory Tract
- Under 12 hours of the birth of the child, alpha-hemolytic streptococci are present in the throat, pharynx, middle ear, and sinus, i.e. upper respiratory tract and these become dominant organisms of oropharynx and remain for life.
- The nasopharynx of the infant is sterile at birth, but within 2-3 days after birth, the infant acquires the flora carried by the mother and attendants the pathogens such as Streptococcus pneumoniae and Neisseria meningitides may be found in the nasopharynx.
- The nose is the natural home of Staphylococcus aureus.
- In the throat, Streptococcus viridians and Neisseria catarrhalis are commonly seen. Pneumococci and Friedlander’s bacillus are also frequently present.
- Occasionally Pseudomonas aeruginosa, E. coli, and Proteus species are also seen in the throats of normal individuals.
- Other communal flora of the upper respiratory tract includes non-pathogenic corynebacteria and Haemophilus spp.
- In health, these endogenous organisms are unable to gain access to tissues and do not cause disease because there is an effective array of defense mechanisms.
- Trachea, bronchi, and lungs, i.e. lower respiratory tract is normally sterile.
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