NORMAL MICROBIAL FLORA OF HUMAN BODY

C.SWAMINATHAN Assistant Professor of Microbiology

Vivekanandha College of Arts and Sciences (Autonomous) for Women

Tiruchengode – 637 205 Tamilnadu, South India

The term ‘normal flora’ denotes the population of microorganisms that inhabit the skin and mucous membrane of normal healthy individuals 1) Resident Flora:Constitute a constant population Cannot be removed completely 2) Transient Flora:Consists of non-pathogenic or potentially pathogenic microbes Derived from the environmentInhabit the skin or mucous membrane for hours, days or weeks

ROLE OF NORMAL MICROBIAL FLORA Advantages

They prevent or suppress the entry of pathogensProduce vitamin K and vitamin BRaise the overall immune status of the host against pathogens having related or shared antigensThe antibiotic substance produced by some, for example, colicins have a harmful effect on pathogensEndotoxins liberated by normal flora may help the defence mechanism of the body

DisadvantagesThey become pathogenic when the immunity is loweredAct as pathogens in tissues outside their habitat. e.g. normal flora of intestine may cause UTICause confusion in diagnosis due to their ubiquitous presence and their resemblance to some of the pathogens

SKIN Staphylococcus epidermidis Staphylococcus hominis Staphylococcus haemolyticus Staphylococcus capitis Streptococcus pyogenes Micrococcus luteus Corynebacterium xerosis Peptostreptococcus spp

Propionibacterium spp Clostridium perfringens Candida albicans Malassezia furfur

CONJUNCTIVA Relatively free from microorganisms due to the flushing action of tears and presence of lysozyme in tears

Corynebacterium xerosis Moraxella spp Staphylococcus spp Non haemolytic Streptococci

NOSE, NASOPHARYNX AND SINUSES

Corynebacterium sppStaphylococcus sppStreptococcus sppHaemophilus sppMoraxella lacunataP.aeruginosa, E.coli, Proteus spp – occasionally found

MOUTH AND UPPER RESPIRATORY TRACT Mouth

Pigmented and non pigmented micrococciGram+ aerobic spore bearing bacilliColiforms, Proteus, Lactobacilli Gum pockets and TonsilsAnaerobic micrococci, Anaerobic streptococciVibrios, Fusiform bacilli, Corynebacterium sppActinomyces, MycoplasmaNeisseria, Bacteroides

GASTROINTESTINAL TRACT GI of foetus is sterile. It becomes contaminated with organism shortly after birth

Breast fed children Lactobacillus bifidus Enterococci Colon bacilli Staphylococci Bottle fed children Lactobacillus acidophilus Enterococci Colon bacilli

Stomach – pH is low – sterile Small intestine Lactobacilli Streptococci Enterobacteria Bacteroides

Large intestine Anaerobic streptococci Anaerobic lactobacilli Clostridium spp, Bacteroides spp, Coliforms Enterococci Proteus Pseudomonas Candida

GENITOURINARY TRACT M.smegmatis – genitalia of male and female

Microflora of genitalia of men Lactobacilli Gardnerella vaginalis Alpha haemolytic streptococci Bacteroides spp Chlamydia trachomatis Ureaplasma urealyticum

Microflora of vagina Lactobacilli, Bifidobacterium Peptostreptococcus, Propionibacterium

Staphylococcus, Streptococcus Corynebacterium, Neisseria, Haemophilus, Enterobacteriaceae

Non pathogenic Treponema Candida spp