By Kristina Fiore, Staff Writer, MedPage Today
Published: May 02, 2012
Reviewed by Robert Jasmer, MD; Associate Clinical Professor of Medicine, University of California, San Francisco.Take Posttest
The bacteria that inhabit the vagina appear to vary greatly from woman to woman, researchers found.
While some women have a stable population of vaginal bacteria, others have more rapid turnover, Jacques Ravel, PhD, of the University of Idaho, and colleagues reported in Science Translational Medicine.
Changes tend to coincide with menstrual periods and sexual activity, but there were “plenty of exceptions,” Ravel told reporters during a telephone briefing.
“The type and abundance of bacteria found in the vagina vary over a short time interval in some, and in others it tends not to change,” he said. “When it comes to the vaginal microbiome, not all women are the same.”
Ravel said the findings challenge older results that focused only on cross-sectional assessments of vaginal bacteria and relied on older methods of assessing bacteria, such as cell culture, that limited the types that could be detected.
It’s long been thought that these bugs protect against infection, largely via the Lactillus genus that produces lactic acid and keeps the pH of the vagina acidic. Yet little is known about whether these bacterial communities vary over time.
So Ravel and colleagues used genomics technologies to sequence the RNA of vaginal bacteria and see whether they change or remain stable.
They enrolled 32 healthy women who conducted vaginal swabs over 16 weeks and kept a daily event diary that was mailed along with the samples to the lab on a weekly basis.
The authors found that most women fell into one of five community types, which is the species composition and abundance of a vaginal community at a specific point in time. Three community types were dominated by the Lactobacillus species crispatus, gasseri, or iners.
Other communities were more heterogeneous in composition. One contained high proportions of Lactobacillus species, but also had some anaerobic bacteria such as Anaerococcus, Corynebacterium, Finegoldia, or Streptococcus. The other type was dominated by the genus Atopobium, along with Prevotella, Parvimonas, Sneathia, Gardnerella, Mobiluncus, or Peptoniphilus.
They found that colonization over time was “complex and somewhat individualized.” Although many women experienced marked changes in bacterial composition over even short periods of time, others had more stable bacterial communities or showed more predictable changes.
Both menstrual periods and sexual activity appeared to be associated with changes in bacterial populations — the latter being a stronger driver of microbial change — but this also was inconsistent among women, Ravel said. Thus, other “unknown factors are certainly at play,” the group wrote.
Exactly what those factors are needs to be the subject of future research, he said. A better understanding of these changes could offer a more personalized treatment strategy for women with conditions such as bacterial vaginosis, he said.
It would not only increase diagnostic accuracy, but could also offer a means of predicting susceptibility and risk of infection, Ravel said.
“We can develop multiple probiotics … that will do a more effective job of covering the diversity of women found in the general population,” Larry Forney, PhD, a co-author on the paper also from the University of Idaho, said during the briefing.
Jill Rabin, MD, of Long Island Jewish Medical Center in New Hyde Park, N.Y., told MedPage Today that more individualized treatment could be useful, although current treatment with antibiotics and then probiotics works for most patients.
“As long as that pH is low, it doesn’t matter if there’s an ‘imbalance’ in bacteria, they’re not going to have symptoms of an infection,” Rabin said.
Ravel added that the work is part of the National Institutes of Health Human Microbiome Project.
The study was supported by the NIH. The researchers reported no conflicts of interest.
Primary source: Science Translational Medicine
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