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 H2O2 and lactic acid suggests that biofilm formation contributes to the survival of G. vaginalis in the presence of lactobacilli.