Can Men Contract Bacterial Vaginosis from Female Partners?
Men cannot "get" bacterial vaginosis in the traditional sense because BV is a condition specific to the vaginal environment, but recent high-quality evidence demonstrates that male partners harbor BV-associated bacteria and treating them significantly reduces recurrence in women. 1
Understanding BV Transmission Dynamics
The Traditional View vs. New Evidence
The longstanding CDC position has been that BV is not a classic sexually transmitted infection and that treating male partners does not prevent recurrence. 2, 3 This recommendation was based on six older randomized trials that consistently showed no benefit to partner treatment. However, a critical 2025 landmark trial in the New England Journal of Medicine fundamentally challenges this paradigm. 1
What the Highest Quality Evidence Shows
The 2025 StepUp trial—the single most recent and highest quality study—demonstrated that treating male partners with combined oral metronidazole 400 mg twice daily plus topical 2% clindamycin cream to penile skin for 7 days reduced BV recurrence from 63% to 35% within 12 weeks (absolute risk reduction of 2.6 recurrences per person-year, P<0.001). 1 This trial was stopped early by the data safety monitoring board because treating women alone was clearly inferior to treating both partners. 1
The Biological Mechanism
- BV-associated bacteria (including Gardnerella vaginalis, Prevotella species, and Mobiluncus species) have been isolated from the male genital tract, particularly on penile skin. 1, 4
- Sexual exchange of these organisms between partners occurs, with evidence suggesting both male-to-female and female-to-male transmission patterns. 1, 4
- The high concordance rates of G. vaginalis carriage among couples supports bacterial exchange during sexual activity. 4
Clinical Implications for Practice
The Sexual Enhancement Model
BV should be understood as a "sexually enhanced disease" rather than a classic STI. 4 This means:
- Women who have never been sexually active rarely develop BV. 2, 3
- BV is associated with multiple sex partners and frequency of intercourse. 2, 4
- Both penetrative and non-penetrative sexual contact (including digital-genital contact and oral sex) enhance BV development. 4
- The mechanism likely involves both alkalinization of the vaginal environment from semen and mechanical transfer of perineal bacteria during coitus. 4
Why Previous Studies Failed
A 2012 systematic review identified critical flaws in all six older trials that formed the basis for the "don't treat partners" recommendation: 5
- Deficient randomization methods
- Suboptimal treatment regimens in women (5 of 6 trials)
- No assessment of treatment adherence
- Insufficient statistical power
- No evaluation of whether antibiotics affected penile microbiota 5
These methodological limitations explain why earlier studies failed to detect a benefit that the 2025 high-quality trial clearly demonstrated. 1, 5
Recurrence Rates and Partner Treatment
- Without partner treatment, 50-80% of women experience BV recurrence within one year. 3, 6
- The 2025 trial showed partner treatment reduced 12-week recurrence from 63% to 35%. 1
- A 2016 Cochrane review of older trials found no benefit, but this predates the 2025 landmark study and included the methodologically flawed trials. 7
Practical Treatment Approach
When to Treat Male Partners
Based on the 2025 NEJM trial, male partners of women with recurrent BV should receive treatment: 1
- Metronidazole 400 mg orally twice daily for 7 days
- PLUS 2% clindamycin cream applied to penile skin twice daily for 7 days 1
Important Patient Counseling
- Both partners must avoid all alcohol during metronidazole treatment and for 24 hours after completion to prevent disulfiram-like reactions. 8, 9
- Refrain from unprotected intercourse for at least 14 days to allow treatment to take effect. 8
- Male partners may experience mild gastrointestinal upset, nausea, headache, or metallic taste. 8, 1
Common Pitfalls to Avoid
- Do not rely solely on older CDC guidelines that predate the 2025 evidence. The treatment landscape has fundamentally changed. 1
- Do not treat male partners with oral antibiotics alone—the combination of oral plus topical therapy was what proved effective. 1
- Do not assume condom use alone will prevent recurrence—while slightly protective, it does not eliminate risk. 4