An adherent Gardnerella vaginalis biofilm persists on the vaginal epithelium after standard therapy with oral metronidazole

OBJECTIVE: The purpose of this study was to determine the efficacy of standard treatment with oral metronidazole in the eradication of the bacterial vaginosis biofilm. STUDY DESIGN: We conducted an interventional follow-up study in which 18 patients with bacterial vaginosis were treated with oral metronidazole during 1 week and subsequently had a single random follow-up assessment at 1-week intervals, up to 5 weeks, with 3 patients representing each point in time. Follow-up assessment included conventional scoring of the vaginal microflora and determination of bacterial biofilm characteristics on a vaginal biopsy through bacterial 16/23S recombinant DNA-based fluorescence in-situ hybridization. RESULTS: Although all patients recovered, we consistently observed the resurgence with treatment cessation of a dense and active bacterial biofilm on the vaginal mucosa, primarily consisting of Gardnerella vaginalis and Atopobium vaginae. CONCLUSION: A large reservoir of the core bacteria to bacterial vaginosis persists as a biofilm after metronidazole treatment.