Sex work is associated with increased vaginal microbiome diversity in young women from Mombasa, Kenya

BACKGROUND: While non-optimal vaginal bacteria and inflammation have been associated with increased HIV risk, the upstream drivers of these phenotypes are poorly defined in young African women.

SETTING: Mombasa, Kenya.

METHODS: We characterized vaginal microbiome and cytokine profiles of sexually active young women aged 14-24 years (n=168) in three study groups: those engaging in formal sex work, in transactional sex, and non-sex workers. Vaginal secretions were collected via self-inserted SoftCup, and assayed for cytokines and vaginal microbiome via multiplex ELISA and 16S rRNA sequencing, respectively. Epidemiological data were captured using a validated questionnaire.

RESULTS: The median age of participants was 20 (IQR: 18-22). Approximately two-thirds of young women (105/168) had vaginal microbial communities characterized by Gardnerella and/or Prevotella spp.-dominance; a further 29% (49/168) were predominantly Lactobacillus iners. Microbiome clustering explained a large proportion of cytokine variation (>50% by the first 2 principle components). Age was not associated with vaginal microbial profiles in bivariable or multivariable analyses. Women self-identifying as sex workers had increased alpha (intra-individual) diversity, independent of age, recent sexual activity, HIV and other STIs (beta = 0.47, 95% CI: 0.05 - 0.90, p = 0.03). Recent sex (number of partners or sex acts last week, time since last vaginal sex) correlated with increased alpha diversity, particularly in participants who were not involved in sex work.

CONCLUSION: Non-optimal vaginal microbiomes were common in young Kenyan women and associated with sex work and recent sexual activity, but independent of age. Restoring optimal vaginal microflora may represent a useful HIV prevention strategy.