Antifungal activity of dual combination of hydroxychavicol with commercialized agents against oral Candida species

Candida spp. is the most prevalent species causing systemic fungal infections. The effect of antifungal agents were screened in vitro and their synergism effect were determined between hydroxychavicol (HC) in association with commercialized antifungal drugs—amphotericin B (AMB), and 5-fluorocytosine (5-FC) alone and in combination against five different oral Candida spp. in their planktonic states at different ratio (1:1 v/v; 1:2 v/v and 2:1 v/v). In vitro susceptibilities of Candida spp. to HC and commercialized antifungal agents were investigated by broth microdilution method as described by Clinical and Laboratory Standards Institute M38-A2. The intensity of the interactions was evaluated by visual reading and spectrophotometric method in checkerboard microdiluton assay, and the nature of the interactions was assessed by fractional inhibitory concentration index. The minimum inhibitory concentration (MIC(50)) of HC, AMB and 5-FC alone against five different planktonic oral Candida spp. ranged from 240 to 120, 8 to 15, and 2 to 8 µg/mL respectively. Positive synergistic effect existed between HC and AMB at 1:1 ratio in all Candida spp. However, there was no synergy effect observed in the majority of Candida spp. for the combination of HC with 5-FC. The data of combination between HC with AMB may be useful in the treatment of systemic infections caused by oral Candida spp. instead of the combination of HC with 5-FC.