When the vaginal microbiome gets out of whack, it causes an uncomfortable, often chronic condition known as bacterial vaginosis, which is associated with pregnancy complications such as premature birth as well as a heightened risk of contracting sexually transmitted diseases. But finding ways to return the disrupted vaginal microbiome to its normal, healthy state has proven difficult because nobody knows what ‘normal’ really means.
As Nature Medicine reported in a July 2011 news feature, a team of scientists at the University of Maryland School of Medicine in Baltimore had found that there are many naturally occurring versions of the microbiome, in part because the bacteria present in a woman’s vagina may vary according to her ethnicity. In a paper published today in the journal Science Translational Medicine, the same team goes on to show that although ethnicity can predict the make up of a the vaginal microbiome over a lifetime, in individual women this bacterial community can change dramatically within a matter of days—often without causing any effects on health.
To characterize this microbial variability, the scientists recruited 32 healthy volunteers for a labor-intensive study. The women enrolled, half of whom were black and half of whom were white, self-sampled vaginal swabs twice a week for more than three months and sent them off to the lab of lead author Jacques Ravel and his collaborator, Larry Forney of the University of Idaho in Moscow. There, biologists sequenced the genomes of the bacteria present in the samples to determine the relative abundance of, for example, the common bacteria species Lactobaccilus or Anaerococcus. For each woman, a picture emerged of a unique and surprisingly mercurial bacterial community. “There has been an assumption that microbiomes are stable over time,” says Forney. “But we found that over the course of just a few days, the entire microbial community could change in a given woman.”
These findings could help biologists develop personalized treatments for bacterial vaginosis, yeast infections and other conditions in which the microbiome is disturbed. “Right now, the antibiotic and probiotic treatments that exist for these diseases work for some women but not for others, and that’s because we don’t understand the environment we’re trying to treat,” says Forney. The hope, he and his colleagues say, is that these findings will lead to new treatments tailored to specific groups of women.
To move toward that goal, they have already begun enrolling more than 160 women to take daily vaginal samples for a larger, more rigorous study of how the various ‘normal’ microbiomes they identified in today’s paper change when a healthy woman develops a vaginal infection. “We need to start rethinking the idea of personalized treatment for diseases of the vagina,” says Ravel.
To read ‘The Vagina Catalogues’ click here.
Artwork by Alyssa Grenning