Contraceptive rings promote vaginal lactobacilli in a high bacterial vaginosis prevalence population: A randomised, open-label longitudinal study in Rwandan women

Abstract

Background: Hormonal contraception has been associated with a reduced risk of vaginal dysbiosis, which in turn has been associated with reduced prevalence of sexually transmitted infections (STIs), including HIV. Vaginal rings are used or developed as delivery systems for contraceptive hormones and antimicrobial drugs for STI and HIV prevention or treatment. We hypothesized that a contraceptive vaginal ring (CVR) containing oestrogen enhances a lactobacilli-dominated vaginal microbial community despite biomass accumulation on the CVR's surface.

Methods: We enrolled 120 women for 12 weeks in an open-label NuvaRing® study at Rinda Ubuzima, Kigali, Rwanda. Vaginal and ring microbiota were assessed at baseline and each ring removal visit by Gram stain Nugent scoring (vaginal only), quantitative PCR for Lactobacillus species, Gardnerella vaginalis and Atopobium vaginae, and fluorescent in situ hybridization to visualize cell-adherent bacteria. Ring biomass was measured by crystal violet staining.

Results: Bacterial vaginosis (BV) prevalence was 48% at baseline. The mean Nugent score decreased significantly with ring use. The presence and mean log10 concentrations of Lactobacillus species in vaginal secretions increased significantly whereas those of G. vaginalis and presence of A. vaginae decreased significantly. Biomass accumulated on the CVRs with a species composition mirroring the vaginal microbiota. This ring biomass composition and optical density after crystal violet staining did not change significantly over time.

Conclusions: NuvaRing® promoted lactobacilli-dominated vaginal microbial communities in a population with high baseline BV prevalence despite the fact that biomass accumulated on the rings.

Fig 1. Participant flow.

N = number of participants, * 1 discontinued after one cycle of vaginal ring use.

Fig 2. Evolution over time of the mean vaginal Nugent score, the mean composite qPCR vaginal health score of vaginal specimens, and the mean composite qPCR vaginal health score of contraceptive vaginal ring biomass.

The Y axis is a score from 0 to 10 for both the Nugent and the composite qPCR vaginal health score. RSV1: first ring removal visit; RSV2: second ring removal visit; LRV: last ring removal visit ____: mean Nugent score _ _ _: mean composite qPCR vaginal health score of the vaginal specimens ……: mean composite qPCR vaginal health score of the contraceptive vaginal rings The composite qPCR vaginal health score is calculated as log₁₀ (Lactobacillus spp.)-log₁₀ (G. vaginalis+ A. vaginae).

Fig 3. Scanning electron microscope observation of the biomass accumulated on contraceptive vaginal rings used for three weeks.

Pictures 1a-3a: The contraceptive vaginal ring was used by a woman with a Nugent score of 10 and with presence of Lactobacillus iners, Gardnerella vaginalis and Atopobium vaginae as measured by qPCR. A vaginal biofilm consisting of Gardnerella vaginalis and Atopobium vaginae was identified using fluorescence in situ hybridization. On the ring Lactobacillus species, Gardnerella vaginalis and Atopobium vaginae were detected using qPCR, the crystal violet optical density was 3.7555 Pictures 1b-3b: Biomass on a contraceptive vaginal ring after use by a woman with a Nugent score of 0 and presence of Lactobacillus iners only. No biofilm was visualized using fluorescence in situ hybridization. On the ring Lactobacillus species was detected using qPCR, the crystal violet optical density was 3.7225.

Fig 4. Evolution over time of the density of contraceptive vaginal ring biomass according to the normal, intermediate and BV vaginal microbiome as determined by Nugent scoring.

The Y axis is the optical density of the crystal violet measurements of the contraceptive vaginal rings. RSV1: first ring removal visit; RSV2: second ring removal visit; LRV: last ring removal visit ____: mean optical densities of ring’s biomass collected from women with a normal vaginal microbiota according to the Nugent score (0–3) _ _ _: mean optical densities of ring’s biomass collected from women with an intermediate vaginal microbiota according to the Nugent score (4–6) ……: mean optical densities of ring’s biomass collected from women with bacterial vaginosis according to the Nugent score (7–10).