Sex Work Is Associated With Increased Vaginal Microbiome Diversity in Young Women From Mombasa, Kenya

Background:Although nonoptimal 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 3 study groups: those engaging in formal sex work, in transactional sex, and nonsex workers. Vaginal secretions were collected using self-inserted SoftCup, and assayed for cytokines and vaginal microbiome through multiplex ELISA and 16S rRNA sequencing, respectively. Epidemiological data were captured using a validated questionnaire.Results:The median age of participants was 20 years (interquartile range: 18-22 years). 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 principal components). Age was not associated with vaginal microbial profiles in bivariable or multivariable analyses. Women self-identifying as sex workers had increased alpha (intraindividual) diversity, independent of age, recent sexual activity, HIV, and other sexually transmitted infections (beta = 0.47, 95% confidence interval: 0.05 to 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:Nonoptimal 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.