CHICAGO — Despite all the focus on the importance of the microbiome, little of that attention has been paid to the one “down there” — specifically as vaginal microbiota affects symptoms of menopause and risk of urinary tract infections or even cancer, a speaker said here.
While a Lactobacillus-dominant vaginal microbiome is generally considered “healthy,” questions remain about what that actually means for a woman’s vaginal health. Caroline Mitchell, MD, of Harvard Medical School, described it in a talk at the North American Menopause Society (NAMS) annual meeting as whether the vaginal microbiome is a “marker or an effector.”
“Are vaginal lactobacilli a marker of people who are healthy anyway or are lactobacilli creating that healthy environment? [The answer] changes how we think of interventions to promote health after menopause,” she said during her talk entitled “The Vagina Dialogues: Vaginal Microbiota and Menopause.”
Mitchell noted that some estimates indicate about 20%-50% of postmenopausal women still have Lactobacillus-dominant vaginal microbiota, but that research showed that giving women hormonal therapy — whether topical or systemic — increased vaginal colonization with these species.
But she pointed to the paucity of research on the topic, saying that no studies have looked at time since menopause or even the role of a woman’s body mass, so “the question of who gets to keep their lactobacilli after menopause is very open.”
And even then, research so far indicates there is little association with Lactobacillus-dominant vaginal microbiome and improvement in clinical symptoms. Mitchell cited a study that found no real association between genitourinary symptoms of menopause (such as dryness, itch/burn, or pain) and women with Lactobacillus dominant vaginal microbiomes.
She said that this pointed more to Lactobacillus as a marker of vaginal health rather than an effector: “If you had Lactobacillus at the beginning, you kept it, and if you didn’t, you didn’t get it.”
In terms of recurring urinary tract infections, which are a problem for post-menopausal women, Mitchell noted research that found vaginal colonization of Lactobacillus was inversely associated with vaginal colonization of Escherichia coli. One prior study found that in women who received vaginal estradiol versus placebo, it was protective of UTI over 8 months. In the active arm of the trial, lactobacilli went up, while Enterobacteriaceae went down.
“It’s not necessarily causal, but it’s plausible that Lactobacillus could be a protective factor,” Mitchell said.
She also addressed the potential role of the vaginal microbiome in conjunction with the upper reproductive tract, mainly the uterus, and whether lower-tract microbiota are associated with different types of cancer. Mitchell said the only cancer where longitudinal data suggested an association was for HPV. However, she noted a recent study that found women with ovarian cancer had a cervicovaginal microbiome where lactobacilli accounted for less than 50% of the species present.
Having addressed the role that the vaginal microbiome could potentially play in women’s health, the topic then turned to probiotics, which have increased in popularity. But most probiotics do not contain the most common Lactobacillus species and they are not FDA regulated.
“We need to be cautious about probiotic studies, because we all want them to work, but we need to be careful and skeptical,” Mitchell said. “Having appropriate controls is super important and … good, high quality science in the field of probiotics is so necessary, because people want to use them.”
She illustrated the point by asking about studies showing probiotics actually improve symptoms, then showing a slide depicting a cricket — indicating research had been quiet in that field.
“That is the extent of the data,” Mitchell said.
She added that, of the few existing studies on the vaginal microbiome, most have been cross-sectional; longitudinal data are needed for cause and effect in all areas of vaginal microbiome research.
On the horizon, Mitchell cited a phase III trial that has been completed for a “live biotherapeutic,” which would be prescribed by a physician and regulated by the FDA — results of which are expected next year.
“High quality science is necessary,” she said. “We all want [probiotics] to work, because it would be awesome, but the science just needs to be better.” More insights about the vaginal microbiome would also allow for the better design of therapies, and would hopefully “improve women’s health overall,” Mitchell concluded.
This talk was supported by Lupin Pharmaceuticals, Pfizer, and TherapeuticsMD.