Bacterial Vaginosis Is More Complex Than We Thought, OB/GYN Expert Says

New microbiome sequencing data and sexual-transmission evidence are prompting clinicians to rethink how bacterial vaginosis (BV) is diagnosed and treated — a shift that could reshape care for the roughly one in three reproductive-age women who get it each year.

In this article:

• Why standard BV testing may be incomplete
• New evidence on sexual transmission
• What this means for recurrence and treatment
• Why this matters for BV patients

Why Standard BV Testing May Be Incomplete

Kate McLean, MD, MPH, FACOG, chief medical officer at microbiome testing company Evvy, says the medical field has long oversimplified BV — and that the current standard of care still does. Most standard diagnostic tests only screen for a small handful of microbes, she explains, when a much longer list of bacteria can work together to cause the condition. Symptom severity, she notes, may depend not just on which microbes are present, but on their relative amounts and whether protective bacteria are also there.

Lactobacillus crispatus is highlighted as one of the "good" bacteria that keeps the vaginal microbiome balanced — but McLean says standard testing doesn't account for the balance between protective and harmful microbes. In February 2026, Evvy published data identifying six distinct microbial subtypes among people clinically diagnosed with BV, based on metagenomic sequencing of more than 100,000 vaginal microbiome samples. The company positions these subtypes as a complement to, not a replacement for, existing diagnostic criteria.

New Evidence on Sexual Transmission

For decades, BV wasn't widely recognized as sexually transmissible. McLean says that's changed only in the past year or so, pointing to a New England Journal of Medicine study showing that treating male partners at the same time as their female partner significantly cut BV recurrence. She frames this as scientific confirmation of something patients have described anecdotally for years.

Why This Matters

For chronic BV patients, this shift has two practical implications. First, a "normal" or negative standard test doesn't necessarily rule out BV-associated bacteria — more detailed microbiome testing may catch what conventional panels miss. Second, if a partner isn't treated alongside the patient, recurrence risk may stay elevated regardless of how well the initial treatment works. McLean is clear the science is still early-stage, and more research is needed before these insights fully translate into new treatment protocols — but the direction of travel is toward more individualized, partner-inclusive care.

Conclusion

Nothing here changes current clinical guidelines yet. But the growing evidence base — six microbial BV subtypes, confirmed sexual transmission dynamics — signals that "just take metronidazole and hope it doesn't come back" is becoming an outdated framework. Patients with recurrent BV may want to ask their provider about more comprehensive testing and partner treatment options.

Sources

• Contemporary OB/GYN, "Kate McLean, MD, MPH, FACOG: Better understanding bacterial vaginosis" (July 1, 2026): contemporaryobgyn.net