Microbial flora of ENT

Human body is perfect natural habitat for number of microorganisms like bacteria, fungi, yeasts and some viruses which are termed as microflora or resident flora or normal flora of a body. Microflora generally consists of saprophytic microbes which are acquired during and after few days of birth of an individual. Bacteria are predominant normal flora organisms. They have an extraordinary ability to attach and colonize epithelial cells, to multiply and establish in human body. Every human being has specific normal flora and its composition is dependent on health status, diet, age and hormonal activities of that individual. Microorganisms establish harmless and beneficial commensalistic and mutualistic associations with human host. In commensalism, microbe derives nutrition from host and in mutualism both microbe and host are benefitted from each other. Normal flora microorganisms compete effectively for space and nutrient supply thereby limiting the growth of members of microflora as well as inhibiting the growth of new microbes which don't comprise normal flora. They also produce antimicrobial substances like acids or antibiotics during their metabolism which restricts the growth of pathogenic or disease causing microorganisms. Reduction in populations of microflora can promote opportunistic infections in body. Opportunistic pathogens are actually resident microbes which takes an opportunity to induce infection in absence of reduced population and competition for space and nutrients by other microflora. They also cause infection when they get entry into another region of body other than their original niche. Destruction of microflora is hazardous to individual's health and caused by excessive cleaning habits, treatment with broad spectrum antibiotics and development of drug resistance in microbes. Normal flora microbes are also responsible for serious infections in immunocompromised conditions such as in acquired immunodeficiency syndrome (AIDS).

Microflora of ear (E): Cerumen or ear wax present in outer ear traps number of microorganisms and prevent them from entering into inner ear. Cerumen also contains antimicrobial compounds which discourage growth of pathogenic Pseudomonas aeruginosa and Staphylococcus aureus, otherwise outer ear being moist and warm would have been ideal place for microbial growth. Despite Cerumen, external ear contains Staphylococcus epidermidis, Propionibacterium acnes and α-hemolytic streptococci as normal flora. Internal ear, under normal healthy state of individual is free from any microorganisms; reason is that it is closed by membranes and filled with lymph fluid. Middle ear microflora matches microbes of nasopharynx as nasal microorganisms can enter middle ear via Eustachian canal. Otitis media, an infection of middle ear is caused by Haemophilus influenzae received from nasopharynx region.

Microflora of nose (N): Microorganisms entering the nose by breathing in are trapped by mucus. It is secreted by nasal epithelium and contains enzyme lysozyme which functions as bactericidal agent. They are also removed mechanically by ciliated epithelium present in nasal passage. Remaining air flora is swallowed in and destroyed by stomach acid. Despite these effective control measures, nose, nasal cavity and nasopharynx (region above soft palate) consists peculiar microflora. They adhere and colonize epithelial cell layer of mucus membrane, thus avoid washing away by mucus. Nasal region consist of avirulent streptococci, Moraxella lacunata, Micrococcus, Corynebacterium, Staphylococcus, Acinetobacter, Bifidobacterium, Branhamella, Neisseria and Haemophilus spp. as normal flora. Nasopharynx harbors common pathogenic bacteria causing infections of nose, throat, bronchi and lungs. Sometimes, bacteria specific to intestinal tract like Escherichia coli and Proteus spp. are also present.

Microflora of throat (T): Actinomyces, Bacteriodes, Micrococcus, Enterococcus, Bordetella, Corynebacterium, Fusobacterium, Haemophilus, Lactobacillus, Mycobacterium, Neisseria, Peptococcus, Staphylococcus, Streptococcus, Treponema, Klebsiella, Enterobacter, Lactobacillus, Escherichia, Proteus and Veillonella constitute normal flora of throat. Species of some bacteria may turn opportunists provided favorable conditions are emerged; Staphylococcus aureus, S. pneumoniae, S. pyogenes, Bordetella pertussis, Haemophilus influenzae, Mycobacterium gordonae, Neisseria meningitides, Actinomyces israelli, Streptococcus viridians, Corynebacterium diphtheriae, Fusobacterium necrophorum and Bacteriodes coagulans are some of the opportunistic pathogens present in a throat as microflora. Classical and infant meningitis infections caused by N. meningitides and H. influenzae respectively and whopping cough (B. pertussis), diphtheria (C. diphtheriae) are initiated in throat. Lung infectious agents such as Pseudomonas aeruginosa (blue pus infection), K. pneumoniae, streptococci (sinusitis) are passed via throat. β- Hemolytic streptococci responsible for tonsillitis are predominant among opportunistic normal flora. During tonsillitis, they not only infect throat and tonsils but also cause ear infections via Eustachian tube.

Ear, nose and throat are interconnected via nasal passage and Eustachian tube. Therefore for the diagnosis of localized ear, nose or throat diseases; ENT surgeon and clinician would have to look for the presence of opportunistic infectious agents from ear, nose and throat.

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