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New research has found bacterial vaginosis is sexually transmitted, and male partners can help in limiting recurrence of the condition.
Bacterial vaginosis (BV) affects 1 in 4 reproductive-aged women globally. Limited Australian data suggest an estimated prevalence of BV of 12% among young women. BV can be associated with a malodorous discharge but can also be asymptomatic. Regardless of symptoms, it is associated with serious sequelae including preterm birth and miscarriage and an increased risk of acquisition of sexually transmitted infections (STIs) and HIV. Global and Australian guidelines recommend treating women only, with oral or vaginal antibiotics. However, this strategy is associated with recurrence rates of >50%, and up to 60–80% among women with an ongoing partner.
There is a large body of evidence to show that BV has the epidemiology of an STI; it is absent in women who have not initiated sex, is associated with having a new sex partner, and condoms offer protection. Furthermore, BV-associated bacteria have been detected in men at two penile sites: the urethra and on penile skin. While past partner treatment trials did not improve cure, most had significant limitations and importantly, no prior partner treatment trial targeted carriage of BV-associated bacteria at both penile sites; all used oral antibiotics only.
We hypothesised that: (i) reinfection from partners was responsible for the high rates of recurrence; and (ii) that oral and topical antimicrobials may both be needed to clear BV bacteria from the two male genital sites. We conducted a randomised trial to assess if male partner treatment, using a combination of oral and topical antibiotics, administered at the time the female partner was being treated, would decrease BV recurrence over 12 weeks, compared to the current standard practice of treating women only.
Our research
Our study, published in the New England Journal of Medicine, was conducted at Australian sexual health clinics and family planning clinics. Women with BV who reported being in a monogamous relationship with a male partner were offered recruitment and couples were randomly allocated to either receiving concurrent female and male partner treatment (intervention group), or the global standard practice of only treating women (control group).
Women were treated with a first line regimen (400 mg oral metronidazole for 7 days, twice daily or 2% intravaginal clindamycin cream for 7 nights or 0.75% intravaginal metronidazole gel for 5 nights). Men in the intervention group received a combination of two antibiotics: 400 mg oral metronidazole twice daily for 7 days and 2% topical clindamycin cream applied to the glans penis and upper shaft (under the foreskin if uncircumcised) twice daily for 7 days.
Couples were then followed up for 12 weeks, and women attended clinics for BV assessments.
Initially we aimed to recruit 342 couples, but an independent data safety and monitoring board stopped the trial at a planned interim analysis at 164 couples, because of a statistical difference in BV recurrence between the two groups.
In the male partner treatment group, 35% of women (recurrence rate [RR], 1.6 per person-year; 95% confidence interval [CI],1.1 to 2.4) experienced BV recurrence over 12 weeks compared to 63% in the control group (RR, 4.2 per person-year; 95% CI, 3.2 to 5.7). This corresponded to a ~60% reduction in the risk of BV recurrence (hazard ratio = 0.37; 95% CI, 0.22 to 0.61) in the male partner treatment group compared to the female-only treatment group.
The treatment was well tolerated by men, with similar side effects between men and women, and mostly attributable to expected side effects associated with metronidazole. The female partners of men who reported taking all the doses of both treatments had the lowest recurrence rate.
The group of women enrolled in this trial were at high risk of recurrence with > 85% reporting recurrent BV, 80% having uncircumcised male partners and 30% having an intrauterine device (IUD) (all strong risk factors for recurrence). As we saw such high rates of cure in this population, the results are very encouraging, and it is likely that male partner treatment may be even more effective in women with fewer risk factors and partners with optimal adherence.
Our trial was limited to women and their regular male partners and was conducted in Australia. Similar trials are needed in other populations to broaden the scope of people accessing partner treatment and extend our findings.
Implications/next steps
The findings represent a very significant advance for BV cure. We have shown that treating male partners with 7 days of oral and topical antibiotics was associated with far lower rates of BV recurrence than the recommended global practice of only treating women.
These results show that reinfection of women with BV bacteria from untreated male partners is responsible for a significant proportion of BV recurrence and is impeding efforts to achieve a cure. Our approach creates a genuine opportunity to reduce the burden of BV for women.
Our key message for clinicians is that partner treatment is sensitive to adherence. If people miss medication, women will experience lower rates of cure, and couples need to avoid unprotected sex during the treatment period to maximise efficacy.
Our next step is to analyse the novel longitudinal samples from couples in this trial to determine the specific BV organisms that drive recurrence and specifically if there is a profile or agent in males that predicts recurrence in women. This advance would enable us to develop more accurate diagnostic tests, including a new diagnostic tool that, for the first time, could test for BV bacteria in male partners to prevent transmission.
While the trial findings have confirmed that reinfection is a significant driver of treatment failure, it is not the sole cause. Our efforts are currently focused on the smaller group of women who experienced BV persistence immediately after treatment in the absence of resuming sex. IUDs were over-represented in this group, suggesting that BV biofilm may play a key role. These women may benefit from longer courses of antibiotics to eradicate these bacteria, or combinations of therapies, but this remains to be established. Our group is continuing to research this.
We have produced a website to provide information for consumers and health professionals that will help people to prescribe and use male partner treatment correctly. It’s important to recognise that this is a paradigm shift in how BV is discussed between patients and their treating clinicians. Our resources can help people start these conversations to deliver partner treatment, much like it is provided for patients with other STIs.
Dr Lenka Vodstrcil is a Senior Research Fellow, and the Deputy Head and principal epidemiologist in the Genital Microbiota and Mycoplasma Group at the Melbourne Sexual Health Centre, Monash University. Dr Vodstrcil leads a translational research program that integrates epidemiological, microbiological and clinical research to improve sexual and reproductive health outcomes at the individual and population level.
Professor Catriona Bradshaw [MMBS (Hons), PhD, FAChSHM, FAHMS] is a clinician researcher, NHMRC Leadership Fellow and Head of Research Translation and Mentorship at Melbourne Sexual Health Centre, Central Clinical School, Monash University and Alfred Hospital. She leads a program that focuses on translational research to improve treatment and control of STIs, including the development and implementation of resistance and point of care diagnostics, antimicrobial resistance and stewardship in STIs, and interventions to optimise the vaginal microbiome.
The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.
The statements or opinions expressed in this article reflect the views of the authors and do not necessarily represent the official policy of the AMA, the MJA or InSight+ unless so stated.
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