Vaginal microbiota impacts of a Lactobacillus crispatus live biotherapeutic and predictors of colonization in randomized 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, significantly reduced recurrent BV in a phase 2b clinical trial, but efficacy was incomplete. Here, we characterize microbiota and immune effects using multi-omics and define correlates of treatment success. By week 12, an L. crispatus-dominant microbiota was achieved in 30% of LBP recipients compared with 9% of placebo recipients (benefit ratio: 3.31; p < 0.005). This is primarily due to CTV-05, but native L. crispatus strains are also present and increase over time. Inflammatory cytokines decrease in both arms after MTZ but return to baseline in placebo recipients. Successful L. crispatus colonization is associated with pre-MTZ microbiota, baseline inflammatory 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.