Microbiota effects and predictors of Lactobacillus crispatus colonization after treatment with a vaginal live biotherapeutic: results from a randomized, double-blinded, placebo-controlled trial.

Bacterial vaginosis (BV) affects >25% of women worldwide and often recurs after standard-of-care metronidazole (MTZ) treatment. LACTIN-V, a live biotherapeutic product (LBP) containing Lactobacillus crispatus strain CTV-05, reduced recurrent BV in a Phase 2b clinical trial, but efficacy was incomplete. We characterized microbiota and immune effects and correlates of treatment success in trial samples. By week 12, L. crispatus-dominant microbiota was achieved in 30% of LBP recipients compared to 9% of placebo (benefit ratio: 3.31; p<0.005). This effect was mostly due to CTV-05, but native L. crispatus strains were also present and increased over time. Inflammatory cytokines decreased in both arms after MTZ, but returned to baseline in placebo recipients. L. crispatus colonization was associated with pre-MTZ microbiota, baseline cytokine profiles, post-MTZ bacterial load, and clinical and behavioral variables. These findings elucidate LBP microbiota effects and identify predictors of treatment success, informing improved intervention strategies to advance women's health.