Bacterial vaginosis-associated vaginal microbiota is an age-independent risk factor for Chlamydia trachomatis, Mycoplasma genitalium and Trichomonas vaginalis infections in low-risk women, St. Petersburg, Russia

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The large majority of studies investigating associations between bacterial vaginosis (BV) and sexually transmitted infections (STIs) have been conducted among predominantly young women with high risk for STIs. Since a risky sexual behavior is a significant risk factor for both STIs and BV, this creates a bias toward an increased association between BV and STIs. This study evaluated associations between BV-associated vaginal microbiota and STIs (Chlamydia trachomatis, Mycoplasma genitalium, Trichomonas vaginalis, and Neisseria gonorrhoeae) in a population of women with low risk for STIs and investigated STI outcomes depending on the dominating Lactobacillus species. Repository cervicovaginal samples collected from reproductive-age women from January 2014 to February 2019 were characterized for vaginal microbiota types and the STIs using multiplex real-time PCR assays. In total, 95 STI-positive and 91 STI-negative samples were included. A significant, age-independent association between BV-associated vaginal microbiota and the presence of C. trachomatis, M. genitalium, and T. vaginalis infections was identified (age-adjusted odds ratios 2.92 [95% confidence interval (CI) 1.24–7.03], 2.88 [95% CI 1.19–7.16], and 9.75 × 107 [95% CI 13.03-∞], respectively). Normal vaginal microbiota dominated by Lactobacillus crispatus, L. gasseri, or L. jensenii was a strong protective factor against C. trachomatis and/or M. genitalium infections, whereas L. iners-dominated microbiota was not significantly associated with C. trachomatis and/or M. genitalium positivity. The results of the present study confirm that STI prevention strategies should include interventions that also reduce the incidence of BV and promote a protective vaginal microbiota in both high- and low-risk women.