Scientists investigate the bacteria that dwell in the human vagina

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Every woman is unique -- and the microbial communities that inhabit her vagina are pretty specialized too.

In a study published online the week of May 31 in Proceedings of the National Academy of Sciences, a group of researchers from several institutions examined the populations of bacteria in the vaginas of nearly 400 healthy, sexually active women. The sample represented four different ethnic groups -- white, black, Latino and Asian -- roughly equally.

Just as our guts are populated with bacteria that are beneficial to human digestion, the human vagina plays host to a rich microbial community. Many of these bacteria produce lactic acid, which can be useful for warding off infections. Prevailing wisdom stated that the microbial makeup of women’s vaginas would vary in relation to how healthy they were -- a healthier woman would have more lactic-acid-producing bacteria. Instead, the researchers were surprised to learn that the microbial communities could be grouped into five different categories, and that the proportions of different bacteria in each of those communities varied according to ethnicity, not level of health.

“Even microbes that were previously believed to be detrimental to a woman’s health seem to be part of a normal ecosystem in some women, according to this study,” said study coauthor Jacques Ravel, who is associate director of the Institute for Genome Sciences at the University of Maryland School of Medicine, in a press release.

To what might the woman-to-woman differences be due?

That’s unknown, the authors write, but ‘it is tempting to speculate that the species composition of vaginal communities could be governed by genetically determined differences between hosts. These might include differences in innate and adaptive immune systems, the composition and quantity of vaginal secretions and ligands on epithelial cell surfaces, among others. Although these may be key to shaping vaginal communities, previous studies have also shown that human habits and practices, including personal hygiene, methods of birth control, and sexual behaviors, also exert strong influences.’

Ravel said this discovery could lead to more personalized medicine for women.

For more information about the scientists’ work and the microbes that inhabit this part of the human anatomy, check out the research paper.

-- Amina Khan