ABSTRACT
Objective To investigate the in vitro anti-candidal activity of the essential oil of Illicium verum (EOIV) alone and in combination with fluconazole. Methods The minimum inhibitory concentration (MIC) and the minimum fungicidal concentration (MFC) of EOIV were determined in 130 clinically isolated Candida strains by NCCLS-M27-A microdilution method, and fluconazole was used as positive control. Meanwhile the checkerboard microdilution method was applied to assay the combined effect of EOIV and fluconazole in 18 candidal strains. Results For the 18 candidal strains the MICs and the MFCs of EOIV were 1 517.16 ?g/mL and 2 248.55 ?g/mL for C. albicans, 1 169.24 ?g/mL and 2 338.49 ?g/mL for C. glabrata, 1 320.03 ?g/mL and 1 741.79 ?g/mL for C. parapsilosis, 1 203.50 ?g/mL and 2 407.01 ?g/mL for C. tropicalis, 1 516.32 ?g/mL and 2 144.40 ?g/mL for C. krusei, and 1 072.64 ?g/mL and 2 144.40 ?g/mL for C. guilliermondii, respectively. Significant synergistic and additive effects were observed after the combination of EOIV with fluconazole, and no antagonism was found. There was no significant difference in the mean fractional inhibitory concentration index (FICI) between the fluconazole-susceptible and the fluconazole-resistant candidal strains (P = 0.671). Conclusion EOIV has antifungal effects on medically important Candida spp.. The combination of EOIV with fluconazole presents a synergistic and additive effects.