Vaginal flora

Vaginal flora or vaginal microbiota are the microorganisms that colonize the vagina. It was discovered by the German gynecologist Albert Döderlein in 1892., and are part of the overall human flora. The amount and type of bacteria present have significant implications for a woman's overall health. The primary colonizing bacteria of a healthy individual are of the genus Lactobacillus, such as L. crispatus, and the lactic acid they produce is thought to protect against infection by pathogenic species.

The primary colonizing bacteria of a healthy individual are of the genus Lactobacillus. Since the first description of lactobacilli by Döderlein, lactobacilli have been generally considered as the gatekeepers of the vaginal ecosystem. Lactobacilli have been shown to inhibit in vitro growth of pathogenic microorganisms, e.g. Bacteroides fragilis, Escherichia coli, Gardnerella vaginalis, Mobiluncus spp., Neisseria gonorrhoeae, Peptostreptococcus anaerobius, P. bivia and Staphylococcus aureus. It is generally accepted that this is achieved mainly through the action of lactic acid. Moreover, lactobacilli normally help to prevent long-term colonization of the vagina by adhering to vaginal epithelial cells. This usually reduces pathogens from infecting to the vaginal epithelium.

Next to lactic acid production and competition for adherence, other antagonistic mechanisms include hydrogen peroxide (a broad-spectrum antimicrobial) and bacteriocins (target-specific antimicrobials) production.

Low pH is generally accepted to be the main mechanism controlling the composition of the vaginal microflora. Although the lactic acid produced by lactobacilli contributes to the vaginal acidity, it is still not proven to be the primary source of low vaginal pH, but the fact remains that most lactobacilli thrive best at a pH < 4.5 .

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