Background A randomised trial of monthly periodic presumptive treatment (PPT) with intravaginal metronidazole 750 mg plus miconazole 200 mg reduced bacterial vaginosis (BV) by 35% compared to placebo. We further assessed the effect of the intervention on detection of select bacterial species in the vaginal microbiome.

Methods HIV-uninfected, non-pregnant women aged 18–45 years from the US and Kenya were randomised to receive PPT or matching placebo for 5 consecutive nights each month for 12 months. Vaginal fluid specimens were collected every other month using Dacron swabs and tested using species-specific quantitative PCR assays that target the 16S rRNA gene. Relative risks [RR] were generated using generalised estimating equations with a log link and exchangeable correlation structure to separately assess the effect of the intervention on species detection.

Results Of 234 women enrolled, 221 (94%) had specimens for analysis (PPT n = 110; placebo n = 111). The proportion of follow-up visits with individual species detected was lower in  the PPT arm versus placebo for: BVAB1 (13.8% vs. 23.7%;  RR = 0.60, 95% CI 0.39–0.93), BVAB2 (30.7% vs. 42.5%; RR = 0.72; 95% CI 0.55–0.95), BVAB3 (22.9% vs. 31.0%; RR = 0.75, 95% CI 0.54–1.03), Atopobium vaginae (59.7% vs. 72.7%; RR = 0.82, 95% CI 0.71–0.94), Leptotrichia/Sneathia (49.4% vs. 60.6%; RR = 0.81, 95% CI 0.68–0.97), and Megasphaera species (26.8% vs. 43.8%; RR = 0.61, 95% CI 0.46–0.82). Lactobactillus crispatus and L. jensenii were more frequently detected in the PPT arm (L. crispatus: 31.8% vs. 26.7%, p = 0.19; L. jensenii: 31.8% vs. 25.1%; p = 0.07). However, these increases were not statistically significant. The prevalence of Gardnerella vaginalis and L. iners during follow-up was high (90% and 91%, respectively) and did not differ by arm.

Conclusions Use of monthly PPT for one year significantly reduced BV prevalence as well as colonisation with a number of bacterial species strongly associated with BV. The role of PPT to improve vaginal health should be considered.

Disclosure of interest statement R. S. M. has received honoraria for invited lectures and consulting as well as donated study product for this trial from Embil Pharmaceutical Company. R. S. M. currently receives research funding from Hologic/Gen-Probe. J. E. B. received honoraria from Symbiomix, Inc for consulting and donated reagents from Hologic/Gen-Probe. J. S. has received consultancy payments from Akesis, Hologic, Symbiomix, and Starpharma, and has grants/pending grants from Akesis, BD Diagnostic, Hologic, Cepheid, Quidel, Symbiomix, Starpharma, and Viamet. All other authors declare that they do not have a commercial or other association that might pose a conflict of interest.