Experts Urge Changes in the Definition of Bacterial Vaginosis

Sep 13, 2011
Marcia Stone

Lactobacillus and vaginal epithelial cell - CDC

Outdated diagnostic criteria of BV risks unnecessary antibiotic use in a significant number of healthy, young American women.

Far too many American women in their child-bearing years are “misdiagnosed and inappropriately treated with antibiotics,” because of an outdated, oversimplified definition of BV according to experts including William Ledger, MD at Weill Medical College of Cornell University in New York City and his colleagues Xia Zhou, MD and Larry Forney, PhD at the University of Idaho in Moscow.

That definition, “a relative lack of Lactobacillus bacteria in the vagina,” must change to reflect new, more accurate information about vaginal microbiology, they say.

“We now know that the healthy vaginal microbiome can be naturally populated by a variety of microbes. It is simply not reasonable to believe that nearly one-third of young American women have a pathologic condition,” according to Ledger.

Molecular based investigations of the genital tract reveal microbial diversity

Ronald F. Lamont, MD from Wayne State University in Detroit, Michigan agrees, citing recent molecular-based studies of vaginal microbiology which “permits identification of previously under-detected and hence under-appreciated organisms.” These investigations confirm that a substantial proportion of healthy women (7-33%) lack appreciable numbers of vaginal Lactobacillus, “However, finding bacteria other than Lactobacillus as, for example, Gardnerella vaginalis, Peptostreptococcus or Pseudomonas does not necessarily constitute an abnormal state,” he adds, explaining that disease results from interplay between the colonizing microbes –their virulence and their numbers—and the host’s immune system.

Furthermore, biologists know that diversity is a good evolutionary tactic; thus, it’s unlikely that every woman in the world, or even in one room, is colonized by exactly the same kinds of microbes. Moreover, the lower vagina, upper vagina and cervix have different microbial flora, Lamont notes. He also explains that microbial communities are not static, thus information revealed at any given point in time is just a snapshot, G. vaginalis for example is known to gain a transient dominance in healthy women during menstruation because of an increase in vaginal pH.

Time to redefine BV

Ledger calls for an immediate re-examination of the BV diagnostic criteria. “First to go,” he says, is the “cornerstone of the current microbiologic ‘truth,’ which is that healthy women have a plentiful number of hydrogen peroxide (H2O2)-producing Lactobacillus.” Very few strains of Lactobacillus iners, which plays a significant role in the normal vaginal microbiome of North American women, are hydrogen-peroxide producing when compared to other lactobacilli (9% vs. 90% respectively) and this means the notion that oxygen-releasing H2O2 can eradicate ‘anaerobic’ bacterial predators is also in doubt. “It has never been proven that H2O2 even reaches pathogen-inhibiting or killing levels in the vagina,” Ledger explains. Lamont adds that H2O2 might only be a biomarker for protective Lactobacillus, not an active factor in limiting the growth of vaginal anaerobes.

“It’s more important to identify women with real pathogens such as Chlamydia trachomatis or Neisseria gonorrhea and treat them early and adequately rather than focus on something called BV,” Ledger says. Lamont adds that BV really isn’t a single entity but rather a spectrum of subtypes which have different causes and require different treatments, which is why he and his collaborators prefer to use the term “Bacterial Vaginosis Syndrome (BVS).” More accurate diagnostic guidelines based on a combination of cultivation-dependent and –independent studies will help restrict antibiotic use to those women for whom the benefits of therapy outweigh the risks.

Antibiotics kill friend and foe alike

In a broader context, Martin Blaser at New York University Langone Medical Center in New York City, comments that "The assumption that antibiotics are generally safe has led to their overuse." However, “Antibiotics kill the bacteria we want as well as those we don’t want,” he explains, “and early evidence from my lab and others hint that sometimes our friendly flora never fully recovers.”

Yet antibiotics are routinely given to women during pregnancy in developed countries and babies acquire their bacterial partners from their mothers as they pass through the vagina. Thus, each generation may be beginning life with a smaller endowment of protective microbes than the last, eroding our ancient microbial defenses, Blaser says. Not only might the loss of beneficial bacteria increase our susceptibility to infections and disease, he adds, “antibiotic overuse could be fueling the dramatic increase in conditions such as obesity, type 1 diabetes, inflammatory bowel disease allergies and asthma, which have more than doubled in many populations.”

Some bacteria deserve to be killed

Some antibiotic use is appropriate, says Blaser, pointing to the 30% of pregnant women infected with group B Streptococcus, which causes serious infection in about 1 of every 200 newborns. But, he calls for a better assessment of which mothers should be treated and which should not.

Ledger adds that "women with symptoms such as unpleasant vaginal odor and irregular discharge should also be thoroughly evaluated and appropriately treated. Symptomatic bacterial vaginosis is associated with sexual activity, thus these women should also be screened for sexually transmitted diseases (STDs) including gonorrhea, Chlamydia, and vaginal trichomoniasis. If present, they will require different therapies than the ones used for BV." However, Ledger argues against treatment for “asymptomatic women with a Gram-stain diagnosis of BV.”