Temporal dynamics of the vaginal microbiome and host immune markers before, during, and after metronidazole treatment for bacterial vaginosis

ABSTRACT This study analyzed metagenomic and immune marker profiles of seven individuals before, during, and after a 7-day course of metronidazole treatment for bacterial vaginosis (BV). Treatment reduced BV-associated bacteria and immune marker levels, with distinct early (days 1–4) and late (days 5–7) phases. Post-treatment variability in microbial and immune marker profiles demonstrated a rapid resurgence of certain BV-associated bacteria, highlighting the need for additional strategies like probiotics to maintain a healthy vaginal microbiome. The study found significant host and microbial influences on immune response variance, with IP-10 and sEcad highly correlated with the vaginal microbiome. The findings identify the optimal timing for administering live biotherapeutics to restore D-lactic acid-producing Lactobacillus species dominance and underscore the complexity of BV infection and treatment response among different people.IMPORTANCEBacterial vaginosis (BV), a common condition associated with an increased risk of preterm birth and sexually transmitted infections, among others, is characterized by a dysbiotic vaginal microbiome associated with the predominance of a diverse assortment of anaerobic bacterial species. Metronidazole is the first-line treatment recommended by the CDC for BV when patients report symptoms. Despite treatment, BV recurrence is common. There is limited data regarding the effects of oral metronidazole on the vaginal microbiome starting at the initiation of treatment, as most studies have compared measurements taken before and after treatment completion. This study utilized metagenomic sequencing, pan-bacterial qPCR, and immune marker measurements to analyze the longitudinal dynamics of the vaginal microbiome and host immune response before, during, and after metronidazole treatment.