The influence of sexual activity on the vaginal microbiota and Gardnerella vaginalis clade diversity in young women

Objectives To examine the influence of sexual activity on the composition and consistency of the vaginalmicrobiota over time, and distribution of Gardnerella vaginalis cladesin young women. Methods Fifty-two participants from a university cohort were selected. Vaginalswabs were self-collected every 3-months for up to 12 months with 184 specimens analysed. The vaginalmicrobiota was characterised using Roche 454 V3/4 region 16S rRNA sequencing, and G.vaginalis cladetyping by qPCR. Results A Lactobacillus crispatusdominated vaginalmicrobiota was associated with Caucasian ethnicity (adjusted relative risk ratio[ARRR] = 7.28, 95%CI:1.37,38.57,p = 0.020). An L.iners (ARRR = 17.51, 95%CI:2.18,140.33,p = 0.007) or G.vaginalis (ARRR = 14.03, 95%CI:1.22,160.69, p = 0.034) dominated microbiota was associated with engaging in penile- vaginalsex. Microbiota dominated by L.crispatus, L.iners or other lactobacilli exhibited greater longitudinal consistency of the bacterial communities present compared to ones dominated by heterogeneous non-lactobacilli (p<0.030); sexual activity did not influence consistency. Womenwho developedBV were more likely to have cladeGV4 compared to those reporting no sex/practiced non-coital activities (OR = 11.82, 95%CI:1.87,74.82,p = 0.009). Specimens were more likely to contain multiple G.vaginalis cladesrather than a single cladeif women engaged in penile- vaginalsex (RRR = 9.55, 95%CI:1.33,68.38,p = 0.025) or were diagnosed with BV (RRR = 31.5, 95%CI:1.69,586.87,p = 0.021). Conclusions Sexual activity and ethnicity influenced the composition of the vaginalmicrobiota of these young, relatively sexually inexperienced women. Women had consistent vaginalmicrobiota over time if lactobacilli were the dominant spp. present. Penile- vaginalsex did not alter the consistency of microbial communities but increased G.vaginalis cladediversity in young women with and without BV, suggesting sexual transmission of commensal and potentially pathogenic clades.