What Is Normal Flora Of Skin Mouth And Different Types

What Is Flora

Normal flora refers to the population of microorganisms that inhabit the skin and mucous membranes of the normal human body. The normal microbial flora can be divided into two groups.
  1. Resident flora
  2. Transient flora

Resident Flora

It consists of organisms that are regularly present in a particular area and when disturbed it re-establishes itself. For example, Escherichia coli is a normal inhabitant of the intestine.

Transient Flora

It consists of both non-pathogenic and potentially pathogenic bacteria that inhabit the body surface or mucous membrane for a limited period.

Pathogens such as the pneumococcus and the meningococcus may be found Pathogens in the nasopharynx of humans from time to time.

NORMAL FLORA OF THE SKIN

Staphylococcus epidermis and diphtheroid are numerous and most constant in the skin. Other microorganisms include Peptococcus, Streptococci viridans, Enterococcus, Micrococcus, Escherichia coli, Proteus, Candida albicans, and Propionibacterium acne. Penicillin resistant staphylococci are seen in individuals working in hospitals.

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, Staphylococcus epidermidis, Moraxella species, and non- hemolytic streptococci.

NORMAL FLORA OF THE NOSE AND NASOPHARYNX

The flora of the nose harbor diphtheroids, staphylococci, streptococci, and Haemophilus species. The nasopharynx is a natural habitat of the common pathogens which cause infections of the nose, throat, bronchi, and lungs.

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, anaerobic streptococci, fusiform bacilli, corynebacterium species, actinomyces, and Bacteroides.

NORMAL FLORA OF THE UPPER RESPIRATORY TRACT

Alpha hemolytic streptococci are present in the upper respiratory tract. In the pharynx and trachea, the flora is similar to that of the mouth.

NORMAL FLORA OF THE GASTROINTESTINAL TRACT

The bacterial count in the adult duodenum is 10 by power 3 -10 by power 8 per gram, in the jejunum and proximal ileum 10 by power 5 -10 by power 8 per gram, and in the lower ileum and caecum 10 by power 5 -10 by power 8 per gram of contents.

Lactobacilli and enterococci predominate in the duodenum and upper ileum, but in the lower ileum and caecum, the flora resembles the fecal flora. Colon and rectum contain about 10 to the power of 11 bacteria per gram of contents, constituting. 10-20 percent of the fecal mass. The normal flora of the adult colon contains mostly (96-99 percent) anaerobes and only 1-4 percent aerobes.

The anaerobic flora includes Bifidobacteria, anaerobic lactobacilli, Bacteroides species, anaerobic streptococci, and clostridia. Enterococci, coliforms, and a small number of Proteus, Pseudomonas, mycoplasma, lactobacilli, and candida are predominant aerobes present in the normal colon.

NORMAL FLORA OF THE GENITOURINARY TRACT

Mycobacterium smegmatis, a harmless commensal, is found in the secretions (smegma) of the genitalia of both males and females. Strains of Mycoplasma and Ureaplasma are frequently present as part of the normal flora of genitalia of both sexes.

Gardnerella vaginalis, Bacteroides species, and alpha-hemolytic streptococci have been found in the penile urethra. The female urethra is either sterile or contains Staph. epidermidis. At puberty, there is a deposition of glycogen in the vagina and the changes to acid due to the metabolic activity of Doderlien’s bacilli.

The pubertal flora persists throughout the reproductive period till menopause. The normal vaginal flora includes clostridia, anaerobic streptococci, Bacteroides specieS, Gardnerella vaginalis, diphtheroid, listeria, and Candida albicans.

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