Antifungal activities of azole drugs in combination with clove essential oil against Microsporum gallinae

Azole drugs are effective for the treatment of Microsporum gallinae infection but fungal resistance to antifungal drugs, and their adverse reactions are concerns in both veterinary and public health. This study's objective was to investigate the antifungal effects of combining clove essential oil with clotrimazole, ketoconazole, or miconazole against M. gallinae ATCC 90749. Antifungal activity was determined by broth microdilution, checkerboard synergy method, and time-kill tests. The minimum inhibitory concentrations (MICs) of azole drugs and clove essential oil were 0.05 and 64.00 mu g/ml, respectively. Clove essential oil and the azole drugs showed partial synergistic effects with fractional inhibitory concentration (FICI) values of 0.75, and MIC values for clove essential oil (32 mu g/ml) and azole drugs (0.125 mu g/ml) were 2- and 4-times lower in combination, respectively. The time-kill kinetics revealed that the killing effect of the combinations was dose- and time-dependent. Formulated topical solutions of clove essential oil and azole drug combinations showed very strong antifungal activity against M. gallinae ATCC 9074. The results of this study indicated that clove essential oil has the potential to be used in combination with azole drugs for the control of M. gallinae infection.