normal flora

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nor·mal flor·a

(nōr'măl flōr'ă)
Microorganisms that normally reside at a given site and under normal circumstances do not cause disease.
Medical Dictionary for the Health Professions and Nursing © Farlex 2012

normal flora

Microorganisms including bacteria, protozoa, and fungi that are found on or in specific areas of the body. The skin and mucous membranes of the oral cavity, intestines, upper respiratory tract, and vagina have specific, permanent flora. They are harmless, even beneficial, in their usual sites, and they inhibit the growth of pathogens, but they can cause infection if they are introduced into unusual sites. If the proportions of the various microorganisms are disrupted, one species may overgrow, as does Candida when bacterial flora are diminished by antibiotics. Synonym: resident flora See: colitis, pseudomembranous; infection; microorganism

The largest concentration of bacteria in humans is in the colon, where more than 400 genera may coexist. In the colon, anaerobic bacteria outnumber aerobic bacteria 1000:1, and there may be 1011 per g of fecal material. The anaerobic gram-positive lactobacilli may be concentrated in the vagina at the 105 to 108/ml level, but 20% of women have no detectable anaerobes in the vagina. In dental plaque and gingival sulci, the bacteria may reach a concentration of 1012/ml.

See also: flora
Medical Dictionary, © 2009 Farlex and Partners

Normal flora

The mixture of bacteria normally found at specific body sites.
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
Another advantage to the new technique is that the scientists did not have to first genetically modify the bacteria in any way in order for them to incorporate the small molecules, meaning the method should work on naturally occurring bacteria in the human body.
Exposing bacteria in the human body to small, steady doses of antibiotics is an ideal way to promote drug resistance, Thorne and the German researchers agree.