Association Between Vaginal Gram Stain Categories and Cervicitis in Kenyan Women Who Engage in Sex Work

Abstract

Abstract Background Cervicitis is often caused by Chlamydia trachomatis and Neisseria gonorrhoeae, but remains unexplained in approximately half of cases. Studies examining associations between the vaginal microbiota and cervicitis have produced conflicting results. Methods This study analyzed data from a cohort of women who engage in sex work in Mombasa, Kenya (2004-2023). Vaginal microbiota was categorized by Nugent criteria as normal (0-3), intermediate (4-6), or bacterial vaginosis (BV, 7-10). Lactobacillus status by culture was classified as none detected, non-H2O2-producing, or H2O2-producing. Cervicitis was defined as >30 polymorphonuclear cells per high-power field. Modified Poisson regression with generalized estimating equations was used to examine associations between Nugent category, Lactobacillus status, and cervicitis. Results Among 1,615 participants (25,322 visits), cervicitis prevalence was 5.8% with normal microbiota, 9.1% with intermediate microbiota (RR 1.39 [95% CI 1.24–1.56]), and 6.8% with BV (RR 1.14 [95% CI 1.02–1.26]). Cervicitis prevalence also varied by Lactobacillus status: 5.1% with none detected, 8.5% with non-H2O2-producing (RR 1.33 [95% CI 1.18–1.50]), and 11.9% with H2O2-producing Lactobacillus (RR 1.70 [95% CI 1.52–1.90]). Findings remained consistent in multivariable analyses. Conclusion Intermediate microbiota was associated with the greatest cervicitis risk among Gram stain categories, exceeding both normal microbiota and BV. Unexpectedly, cervicitis risk increased progressively from no Lactobacillus to non-H2O2-producing to H2O2-producing Lactobacillus. These findings suggest that intermediate microbiota may represent a state in which proinflammatory pathways from BV and Lactobacillus-dominated microbiota intersect, potentially driving enhanced neutrophil recruitment. Future studies should test this hypothesis.