Sexual practices have a significant impact on the vaginal microbiota of women who have sex with women

Abstract

Women-who-have-sex-with-women (WSW) are at increased risk of bacterial vaginosis (BV). We investigated the impact of practices and past BV on the vaginal microbiota within a two-year longitudinal cohort of Australian WSW. Self-collected vaginal swabs were used to characterise the vaginal microbiota using 16S-rRNA gene sequencing. Hierarchical clustering defined community state types (CSTs). Bacterial diversity was calculated using the Shannon diversity index and instability of the vaginal microbiota was assessed by change of CST and Bray-Curtis dissimilarity. Sex with a new partner increased the bacterial diversity (adjusted-coefficient = 0.41, 95%CI: 0.21,0.60, p < 0.001) and instability of the vaginal microbiota, in terms of both change of CST (adjusted-odds-ratio = 2.65, 95%CI: 1.34,5.22, p = 0.005) and increased Bray-Curtis dissimilarity (adjusted-coefficient = 0.21, 95%CI: 0.11,0.31, p < 0.001). Women reporting sex with a new partner were more likely than women reporting no new partner to have a vaginal microbiota characterised by Gardnerella vaginalis (adjusted-relative-risk-ratio[aRRR] = 3.45, 95%CI: 1.42,8.41, p = 0.006) or anaerobic BV-associated bacteria (aRRR = 3.62, 95%CI: 1.43,9.14, p = 0.007) relative to a Lactobacillus crispatus dominated microbiota. Sex with a new partner altered the vaginal microbiota of WSW by increasing the diversity and abundance of BV-associated bacteria. These findings highlight the influence of practices on the development of a non-optimal vaginal microbiota and provide microbiological support for the sexual exchange of bacteria between women.

Figure 1

The vaginal microbiota of women who have sex with women. The heatmap displays the relative abundance of the 15 most abundant bacteria detected in women in this study. Hierarchical clustering of Euclidean distances with Ward linkage was used to determine eight community state types (CST): CST1-L. crispatus, CST2-Lactobacillus mixed, and CST3-L. iners (n = 93), CST4-G. vaginalis and diverse, CST5-anaerobic and diverse, CST6-L. gasseri, CST7-Bifidobacterium longum, CST8-L. jensenii/L. fornicalis. Exposure to a new sexual partner in the preceding 90 days is indicated above the heatmap.

Figure 2

Longitudinal changes of community state type in women reporting sex with a new partner. Each column represents a participant and sequential longitudinal specimens are ordered from baseline to endpoint. Boxes are coloured according to community state type (CST). *Indicates a report of sex with a new partner. Most women changed CST at least once during the study. Change of CST occurred in 36/40 (90%) women who reported exposure to a new partner and 47/60 (78%) women who did not report sex with a new partner.