Combination of Farnesol with Common Antifungal Drugs: Inhibitory Effect against Clinical Isolates of <em>Candida</em> Species

Abstract: Vulvovaginal candidiasis (VVC) is a mucous membrane infection, with an increased rate of antifungal resistance of Candida species. The in vitro efficacy of farnesol alone or in combination with traditional antifungals, against resistant Candida strains recovered from women with VVC was assessed. In this study, 80 Candida isolats were identified by multi-plex PCR. Antifungal sus-ceptibility of amphotericin B (AMB), fluconazole (FLU), itraconazole (ITZ), voriconazole (VOR), clotrimazole (CTZ) and farnesol was tested by M27-A3/S4 broth micro dilution method. The combinations of farnesol with each antifungal were calculated based on the fractional inhibitor concentration index (FICI). C. glabrata was the predominant species (48.75%) isolated from vaginal discharges, followed by C. albicans (43.75%), C. parapsilosis (3.75%), mixed infection of C. albicans and C. glabrata (2.5%), C. albicans and C. parapsilosis (1%). C. albicans and C. glabrata isolates had lower susceptibility to FLU (31.4% and 23.0%, respectively) and CTZ (37.1% and 33.3%, respectively). Importantly, there was ‟synergismˮ between farnesol-FLU and farnesol-ITZ against C. albicans and C. parapsilosis (FICI= 0.5 and 0.35, respectively), reverting the original azole resistant profile. These findings indicate that farnesol is able to revert to the resistance profile of azole by enhancing the activity of FLU and ITZ in resistant isolates, which is a promising result.