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Even "Healthy" Vaginas Microbiomes Vary

Ashley Yeager

Every woman has a unique vaginal microbiome, according to a new study that could change how doctors diagnose and treat gynecological disease.

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Not all vaginas are created equal, at least in terms of the microbes they harbor.

During a 16-week study, scientists analyzed microbial samples taken from the vaginas of 32 women. In the end, the researchers discovered that not only is each woman’s vaginal microbial community unique but also these microbiomes can change drastically in just days.

Published in Science Translational Medicine (1), the results suggest that doctors need to rethink the commonly held belief that all women have the same bacteria in their vagina. Therefore, it’s unlikely that all women would respond favorably to identical treatments for bacterial vaginosis and other infections of that part of the birth canal.

Characterizing the different vaginal microbial types, represented here, that exist may help doctors develop distinct probiotics to better treat and maintain the health of all women’s reproductive tracts, even though bacterial ecosystems vary. Credit: Jacques Ravel and Larry Forney.

“Without a complete understanding of interactions between our genome and microbial genomes, it is going to be impossible to obtain a complete picture of our biology and translate this to better treatment and diagnosis,” said study co-author Jacques Ravel, a geneticist at the University of Maryland.

Previously, Ravel and others have shown that five distinct types of microbial communities exist in the vagina. These different types often correlate to a woman’s ethnicity. In this new study, Ravel and his colleagues asked 32 women to take swaps of their vagina twice a week for 16 weeks. Each week, the women sent the samples along with a diary of their sexual and hygiene habits to the researchers.

To identify changes in the microbial communities, Ravel and his collaborators sequenced bacterial rRNA genes from the samples. As in previous studies, the scientists characterized each woman's bacterial colony into one of five types based on the different kinds and quantities of each bacteria present.

The most surprising finding was the dramatic day-to-day changes in some of the vaginal microbiomes, Ravel said. "We saw a certain kind of community in one woman. Three days later it was 99% different, a major shift in composition," he said. On the other hand, some women's vaginal composition did not change very much at all. This was the first study to look at women’s vaginal ecosystems over an extended period of time.

“Each woman is telling her own story,” said Larry Forney, a University of Idaho microbial ecologist and Ravel’s co-author.

But despite their microbial differences, the analysis showed that women are still producing the same metabolites. For example, all the samples showed traces of lactic acid.

In the end, the story remains incomplete. Scientists don't know the exact purpose that the vaginal microbes serve, why they vary, or why they produce the same byproducts.

The research is, however, a "gateway" to personalized medicine for women, Forney said. By determining the different vaginal ecosystems that exist and how they vary woman-to-woman, gynecologists could understand what each patient’s “healthy” vaginal colony looks like. Then, in the event of an infection, doctors could more accurately prescribe a probiotic unique to the woman’s microbial make-up, instead of a general antibiotic.

Next Ravel and Forney's team plans to continue their study of vaginal ecosystems by sampling 135 women each day for 10 weeks. The results should clue scientists in to the behavior that causes vaginal bacterial colonies to change and what the microbial community is like just prior to infection.


1. Pawel, G. et al. 2012. Sci Transl Med 4(132): 132ra52

Keywords:  genomes