Retrocyclin inhibits Gardnerella vaginalis biofilm formation and toxin activity

Retrocyclins are cyclic antimicrobial peptides that have been shown to be both broadly active and safe in animal models. RC-101, a synthetic retrocyclin, targets important human pathogens and is a candidate vaginal microbicide. Its activity against microbes associated with bacterial vaginosis is unknown. We investigated the effect of RC-101 on toxin activity, bacterial growth and biofilm formation of Gardnerella vaginalis in vitro. RC-101 potently inhibits the cytolytic activity of vaginolysin, the Gardnerella vaginalis toxin, on both erythrocytes and nucleated cells. RC-101 lacks inhibitory activity against planktonic G. vaginalis but markedly decreases biofilm formation. These dual properties, toxin inhibition and biofilm retardation, justify further exploration of RC-101 as a candidate agent for bacterial vaginosis prevention.