Boys and BV

A recent study published in The New England Journal of Medicine explored the impact of treating male partners in the recurrence of bacterial vaginosis (BV) in women (1).

BV is an incredibly problematic clinical condition globally. It is the most common presentation in women of reproductive age, with 80% of cases recurring within three months of recommended antibiotic therapy (2). In clinical practice, this often presents as a monthly flair or, in some cases, persistent symptoms.

This study took a fresh approach by investigating whether treating male partners with both oral and topical antibiotics could reduce BV recurrence. The results were compelling: when only women were treated, the risk of recurrence within 12 weeks was 63%. However, when their male partners also received oral metronidazole and topical clindamycin for seven days, the recurrence rate dropped to 35%. This randomised controlled trial, involving 164 couples, was stopped early due to the strong evidence supporting male partner treatment.

This finding is a promising step towards a breakthrough in the treatment of BV. By treating male partners concurrently, we see a significant reduction in the recurrence of BV symptoms. This raises the question of whether current treatment guidelines, which typically do not recommend partner treatment, need to be reconsidered. Since institutional guidelines take time to change, individual clinicians may need to decide how to incorporate these findings into their practice.

This reinforces a growing understanding that BV isn’t solely about pH. It’s also influenced by microbial transfer between partners, with sex playing a key role in the recurrence of BV through bacterial exchange and microbiome disruption. A 2020 study identified bacterial species, such as Parvimonas, Lactobacillus iners, L. crispatus, Dialister, Sneathia sanguinegens, and Gardnerella vaginalis, as strong predictors of BV development in female partners (3).

However, one major concern is the way this research is being reported. Many headlines are framing BV as a sexually transmitted infection (STI), which is misleading. While male partners can contribute to recurrence, BV is not exclusively linked to sexual activity. People who are not sexually active—or who have never had sex—can still develop BV. Other factors, such as douching, period blood, immune system challenges, or antibiotic use, can also trigger vaginal microbiome imbalances and lead to BV (4,5).

Research into BV recurrence is critical because a stable vaginal microbiome plays a key role in reproductive and overall health. BV has been linked to pelvic inflammatory disease, miscarriage, early pregnancy loss in IVF, preterm birth, and postpartum complications such as endometritis and wound infections (6,7). It also increases susceptibility to HIV (8), HPV (9), gonorrhoea, and chlamydia (10).

Also, what’s missing from the discussion is that it’s not a given that both partners carry the same bacteria. In clinic, I often see some overlap in bacterial strains, but usually in varying amounts. More often than not, different microbes dominate in the seminal microbiomes, meaning the male partner may require a different treatment approach from his female partner, based on her vaginal or uterine microbiome report. This is why microbiome testing is so important—to determine whether both partners need antibiotics and, if so, whether they require different treatments. Automatically prescribing antibiotics when they’re not necessary can do more harm than good, as they wipe out beneficial bacteria. If that good bacteria isn’t re-established, it can create space for more harmful microbes to take hold instead.

Knowing your vaginal microbiome can help you get to the root of recurring issues. Companies like ScreenMe use next-generation sequencing to provide a detailed analysis of both vaginal and seminal microbiome health.

For women, BV symptoms typically include a thin, white, grey, or green discharge, a fishy odour, elevated vaginal pH, and the presence of 'clue' cells (vaginal lining cells coated with bacteria). Men, on the other hand, often show no symptoms at all—classic!

This study is a promising step forward, but there’s still more to uncover. More research is needed to refine treatment approaches, but one thing is clear: tackling BV requires looking beyond just the female microbiome—because when it comes to recurring infections, it really does take two.

References:

1. Vodstrcil LA, Plummer EL, Fairley CK, et al. Male-Partner Treatment to Prevent Recurrence of Bacterial Vaginosis. N Engl J Med. 2025;392(12):1125-1135. doi:10.1056/NEJMoa2405404.

2. Coudray M, Madhivanan P. Bacterial vaginosis—A brief synopsis of the literature. European Journal of Obstetrics & Gynecology and Reproductive Biology. 2020;245:143-148.

3. Lennon NJ, Patil S, Crossman DK, et al. The microbiome composition of a man's penis predicts incident bacterial vaginosis in his female partner. Front Cell Infect Microbiol.
2020;10:433. doi:10.3389/fcimb.2020.00433.

4. Hickey, R.J., et al. (2012). "Characterization of the vaginal microbiota of women of reproductive age." BMC Microbiology, 12:193. https://doi.org/10.1186/1471-2180-12-193.

5. McClelland, R.S., et al. (2006). "Risk factors for bacterial vaginosis in HIV-1 seronegative women in Nairobi, Kenya." Sexually Transmitted Diseases, 33(8): 493-498. https://doi.org/10.1097/01.olq.0000211367.56946.96.

6. Lewis F, Bernstein K, Aral S. Vaginal Microbiome and Its Relationship to Behavior, Sexual Health, and Sexually Transmitted Diseases. Obstetrics & Gynecology. 2017;129(4):643-654.

7. Sobel J, Sobel R. Current and emerging pharmacotherapy for recurrent bacterial vaginosis. Expert Opinion on Pharmacotherapy. 2021;22(12):1593-1600.

8. Mehta S, Zhao D, Green S, Agingu W, Otieno F, Bhaumik R et al. The Microbiome Composition of a Man's Penis Predicts Incident Bacterial Vaginosis in His Female Sex Partner With High Accuracy. Frontiers in Cellular and Infection Microbiology. 2020;10.

9. Swidsinski A, Doerffel Y, Loening-Baucke V, Swidsinski S, Verstraelen H, Vaneechoutte M et al. Gardnerella Biofilm Involves Females and Males and Is Transmitted Sexually. Gynecologic and Obstetric Investigation. 2010;70(4):256-263.

10. Sanchez S, Garcia P, Thomas K, Catlin M, Holmes K. Intravaginal metronidazole gel versus metronidazole plus nystatin ovules for bacterial vaginosis: A randomized controlled trial. American Journal of Obstetrics and Gynecology. 2004;191(6):1898-1906.