Interaction of eugenol and voriconazole against genital isolate of Candida tropicalis and Candida krusei from the mares

Background and Aim : Due to the limited range of antifungals available to treat genital Candida infections and the emergence of resistant isolates, attention has focused on the antifungal potency of natural compounds with promising biological properties. To examine whether eugenol synergises the in vitro efficacy of voriconazole against Candida strains isolated from the genital tract of mares.Methods : The antifungal activity of eugenol and voriconazole was evaluated using the broth microdilution assay (CLSI‐ M۲۷‐A۳). Synergism of eugenol and voriconazole was evaluated by the microdilution checkerboard methodResults : Minimum inhibitory concentration (MIC) values for eugenol and voriconazole ranged from ۴۰۰ to ۸۰۰ μg/mL and ۱ to ۸ μg/mL, respectively, for C. tropicalis isolates, and from ۲۰۰ to ۴۰۰ μg/mL for eugenol and ۲ to ۱۶ μg/mL for voriconazole against C. krusei isolates. Eugenol decreased the arithmetic mean MIC for voriconazole against C. tropicalis and C. krusei isolates from ۲.۶۶ to ۰.۴۶ μg/mL and ۷.۷۷ to ۰.۴۱ μg/mL respectively. The fractional inhibitory concentration index (FICI) values for the eugenol‐voriconazole combination ranged from ۰.۲۵ to ۰.۸۸ and ۰.۱۹ to ۰.۶۳ for C. tropicalis and C. krusei isolates respectively. A synergistic effect of eugenol in combination with voriconazole was observed for ۸۳.۳% of C. tropicalis and ۷۷.۷% of C. krusei isolates.Conclusion : Eugenol showed fungistatic and fungicidal effects against genital Candida isolates and, in combination, synergised the antifungal effects of voriconazole. The eugenol‐voriconazole combination can lay the foundation for a therapeutic approach against isolates in which azole resistance has increased over time.

Keywords:

Eugenol , voriconazole , antifungal activity , Candida tropicalis , Candida krusei