Effect of biofilm phenotype on resistance of Gardnerella vaginalis to hydrogen peroxide and lactic acid

OBJECTIVE: Bacterial vaginosis is the most common vaginal disorder worldwide. Certain lactobacilli produce H2O2 and lactic acid, which normally suppress growth of anaerobes; however, in bacterial vaginosis, Gardnerella vaginalis and other anaerobes proliferate, and the number of lactobacilli decreases. G vaginalis colonizes the vaginal epithelium as a biofilm, which likely plays a role in colonization and relapsing infection. STUDY DESIGN: We developed an in vitro model for G vaginalis biofilm formation and compared susceptibilities of biofilms vs planktonic cultures to H2O2 and lactic acid. The structure and composition of the biofilm matrix were studied in order to design a method for biofilm dissolution. RESULTS: Biofilms tolerated 5- fold and 4- 8 fold higher concentrations of H2O2 and lactic acid (respectively) than planktonic cultures. Proteolytic dissolution of biofilms reduced sensitivity to H2O2 and lactic acid. CONCLUSION: Increased tolerance to H202 and lactic acid suggests that biofilm formation contributes to the survival of G vaginalis in the presence of lactobacilli.