In vitro activity of verapamil alone and in combination with fluconazole or tunicamycin against Candida albicans biofilms

Calcium channels and pumps play important roles in morphogenesis, stress response and virulence in Candida albicans. We hypothesised that verapamil, a potent calcium channel blocker, may display an inhibitory effect on C. albicans biofilms. To test this hypothesis, the in vitro activity of verapamil was evaluated alone and in combination with fluconazole or tunicamycin against C. albicans biofilms using a 96-well microtitre plate model. As expected, verapamil exerted inhibitory activity against C. albicans biofilms. The combinations of verapamil/fluconazole and verapamil/tunicamycin yielded synergistic effects on biofilm formation and on pre-formed biofilms. Furthermore, verapamil alone or in combination with fluconazole or tunicamycin led to a significant decrease in the transcription level of ALS3, essential for biofilm development. Therefore, verapamil may be a potential agent to enhance the effect of antifungal drugs against C. albicans biofilms.