What data is available regarding partner treatment to prevent recurrence of bacterial vaginosis?

Introduction
Bacterial vaginosis (BV) is the most common cause of vaginal discharge in women of reproductive age, caused by imbalance in vaginal flora, where the normally dominant Lactobacillus species are replaced by more diverse bacterial species, including an overgrowth of anaerobic bacteria.^1-3 The imbalance in the microbiome that occurs with BV increases vaginal pH. Individuals who contract BV may be asymptomatic or have bothersome symptoms that include abnormal or increased vaginal discharge and foul odor. Women with untreated BV have an increased risk of acquiring sexually transmitted infections (STIs) and BV has been associated with increased risk of preterm delivery or spontaneous abortion in women who are pregnant.

Recurrence is also common.^4,5 Up to 50% of women who have had BV experience recurrence within 6 to 12 months of initial infection, even after treatment. The organisms responsible for BV have been isolated from the male penile microbiome in studies and correlate to BV infection in women who have sex with men.^2,3 Because of high recurrence rates, there is increasing attention on male partner treatment as a strategy to reduce recurrence. The purpose of this article is to summarize available evidence on the role of male sexual partner treatment in managing BV recurrence. For the purposes of this article, the terms “woman/en” and “female” will be used when discussing biological sex of a female, including individuals who were assigned female at birth who may no longer identify as women. Similarly, “man/en”, and “male” will be used to denote biological sex of a male, including individuals who were assigned male at birth who may no longer identify as a man.

Sexual transmission and the role of partners
Bacterial vaginosis is not strictly considered an STI, but sexual partner microbiota may contribute to transmission.^2,3 Risk factors for BV include new or multiple male sexual partners, female sexual partners, lack of condom use with male sexual partners, and douching.³ Females who have sex with females have a higher prevalence of BV compared to females who have sex with males, with a high level of BV concordance between same-sex partners.^6-8 However, one study found that monogamous same sex partnerships led to alignment of a stable, favorable vaginal microbiota in couples, adding to data that the original or first infection of BV is sexually transmitted, and new or multiple partners contribute to risk of BV.⁷ Additionally, women who have never been sexually active are rarely affected by BV.³ As mentioned above, the organisms responsible for BV have been isolated from the normal flora of the male genital tract.^2,3 Re-exposure from untreated partners may reintroduce harmful bacteria after initial treatment, which is the rationale for studies involving treatment of male sexual partners.

Review of available evidence on partner treatment
Early randomized controlled trials (RCTs) of sexual partner treatment from the 1980s and 1990s yielded inconclusive or negative results, often due to methodological limitations, including lack of sufficient power due to limited recruitment of patients or lack of information on medication adherence.^5,9,10 Many previous RCTs also used single-agent antibiotic treatment instead of dual-drug regimens. In the past 5 years, there have been limited published data related to male partner treatment to reduce recurrence in female partners. Schwebke et al 2021 conducted a double-blind, placebo-controlled RCT to determine if treatment of male sexual partners of women with recurrent BV would decrease recurrence rates in women.¹¹ Two-hundred fourteen couples were enrolled. All women with BV were treated with guideline-recommended therapy (metronidazole 500 mg orally twice daily for 7 days) and the male partners were randomized to either receive placebo or single-agent antimicrobial therapy (metronidazole 500 mg orally twice daily for 7 days). By 16 weeks, treatment failure had occurred in 81% and 80% of women in the metronidazole and placebo groups, respectively, with no significant difference between groups (p>0.999). In exploratory analyses, women whose male partners adhered to study medication were less likely to fail treatment (relative risk, 0.85; 95% confidence interval [CI], 0.73 to 0.99; p=0.035). Administration of multidose regimens was not studied.

In 2021, a pilot study of 34 heterosexual couples treated for BV demonstrated that dual-antibiotic therapy in male partners (oral metronidazole 400 mg and 2% clindamycin cream topically applied to penile skin, both twice daily for 7 days) significantly reduced BV-associated bacteria, altering the microbiota composition of male genitalia.¹² Suppression of BV-associated bacteria was also sustained in most women over the course of the study. Based on these results, the study group moved forward with the StepUp RCT, which is described in Table 1.

The RCT by Vodstrcil et al 2025 demonstrated that combined oral and topical antimicrobial therapy for male partners of women with BV resulted in a lower rate of recurrence of BV within 12 weeks compared to female treatment only.¹³ The trial was stopped at interim analysis due to the significant differences found between groups. There are some limitations to this trial that may impact its generalizability. The study was conducted in Australia, with slightly differing treatment recommendations for women with BV than in the US (metronidazole 400 mg twice daily in study vs 500 mg twice daily recommended in US guidelines).^3,13 The majority of patients (male and female) in the study were of European or Western Pacific descent, which may not reflect the population of individuals in the US.¹³ Racial and ethnic disparities in the prevalence of BV have been documented, with the prevalence of BV among Black women in the US being particularly high.³ Additionally, the majority of the male partners in both treatment groups (80%) were uncircumcised, which can confer additional risk of BV to female partners.¹³ Finally, only couples who were in monogamous relationships were eligible. Overall, the low BV recurrence rates for women with male partners treated with dual-antimicrobial therapy may be practice changing and act as an additional mechanism to treat recurrent BV in women.

Current guideline treatment recommendations
All available treatment guidelines for BV have been published prior to the publication of the Vodstrcil et al 2025 study and do not include this new data. The Centers for Disease Control and Prevention (CDC) guidelines on sexually transmitted infections treatment were last updated in 2021.³ They recommend treatment for BV in women with symptomatic BV. The recommended first-line treatment includes 1 of 3 treatment options: metronidazole 500 mg orally twice daily for 7 days, metronidazole gel 0.75% administered intravaginally once daily for 5 days, or clindamycin cream 2% administered intravaginally at bedtime for 7 days. The CDC guideline does not currently recommend routine partner treatment for BV. The 2020 American College of Obstetricians and Gynecologists (ACOG) practice bulletin on vaginitis in nonpregnant patients (reaffirmed in 2025) echoes the recommendations made by the CDC, including the lack of recommendation for routine partner treatment for BV.¹⁴

Conclusion
Currently, professional organization guidelines do not recommend the routine treatment of male sexual partners of women with confirmed BV. However, recently published evidence demonstrates that BV recurrence rates of female partners were reduced by nearly half following male partner treatment with dual-antibiotic therapy compared to no treatment. These results may impact treatment recommendations in future updates of clinical guidelines. Additionally, the preponderance of evidence supporting sexual transmission of BV may lead to the reclassification of BV as an STI, which may also alter treatment paradigms.

References

1. Reiter S, Spadt SK. Bacterial vaginosis: a primer for clinicians. Postgrad Med. 2019;131(1):8-18. doi: 10.1080/00325481.2019.1546534
2. Chacra LA, Fenollar F, Diop K. Bacterial vaginosis: what do we currently know? Front Cell Infect Microbiol. 2022;11:672429. doi: 10.3389/fcimb.2021.672429
3. Workowski KA, Bachmann LH, Chan PA, et al. Sexually transmitted infections treatment guidelines, 2021. MMWR Recomm Rep.2021;70(4):1-187. doi: 10.15585/mmwr.rr7004a1
4. Faught BM, Reyes S. Characterization and treatment of recurrent bacterial vaginosis. J Womens Health (Larchmt). 2019;28(9): 1218-1226. doi: 10.1089/jwh.2018.7383
5. Vodstrcil LA, Muzny CA, Plummer EL, Sobel JD, Bradshaw CS. Bacterial vaginosis: drivers of recurrence and challenges and opportunities in partner treatment. BMC Med. 2021;19(1):194. doi: 10.1186/s12916-021-02077-3
6. Evans AL, Scally AJ, Wellard SJ, Wilson JD. Prevalence of bacterial vaginosis in lesbians and heterosexual women in a community setting. Sex Transm Infect. 2007;83(6):470-475. doi: 10.1136/sti.2006.022277
7. Bradshaw CS, Walker SM, Vodstrcil LA, et al. The influence of behaviors and relationships on the vaginal microbiota of women and their female partners: the WOW Health Study. J Infect Dis. 2014;209(10):1562-1572. doi: 10.1093/infdis/jit664
8. Vodstrcil LA, Walker SM, Hocking JS, et al. Incidence bacterial vaginosis (BV) in women who have sex with women is associated with behaviors that suggest sexual transmission of BV. Clin Infect Dis. 2015;60(7):1042-1053. doi: 10.1093/cid/ciu1130
9. Mehta SD. Systematic review of randomized trials of treatment of male sexual partners for improved bacteria vaginosis outcomes in women. Sex Transm Dis. 2012;39(10):822-830. doi: 10.1097/OLQ.0b013e3182631d89
10. Amaya-Guio J, Viveros-Carreño DA, Sierra-Barrios EM, Martinez-Velasquez MY, Grillo-Ardila CF. Antibiotic treatment for the sexual partners of women with bacterial vaginosis. Cochrane Database Syst Rev. 2016;10(10):CD011701. doi: 10.1002/14651858.CD011701.pub2
11. Schwebke JR, Lensing SY, Lee J, et al. Treatment of male sexual partners of women with bacterial vaginosis: a randomized, double-blind, placebo-controlled trial. Clin Infect Dis. 2021;73(3):e672-e679. doi: 10.1093/cid/ciaa1903
12. Plummer EL, Vodstrcil LA, Doyle M, et al. A prospective, open-label pilot study of concurrent male partner treatment for bacterial vaginosis. mBio. 2021;12(5):e0232321. doi: 10.1128/mBio.02323-21
13. Vodstrcil LA, Plummer EL, Fairley CK, et al. Male-partner treatment to prevent recurrence of bacterial vaginosis. N Engl J Med. 2025;392(10):947-957. doi: 10.1056/NEJMoa2405404
14. Vaginitis in nonpregnant patients: ACOG practice bulletin, number 215. Obstet Gynecol. 2020;135(1):e1-e17. doi: 10.1097/AOG.0000000000003604

Prepared by:
Rachel Brunner, PharmD, BCPS
Clinical Assistant Professor, Drug Information Specialist
University of Illinois at Chicago Retzky College of Pharmacy

October 2025

The information presented is current as of September 23, 2025. This information is intended as an educational piece and should not be used as the sole source for clinical decision-making.