A study on the synergism antifungal activity of clotrimazole in combination with berberine hydrochloride against Candida albicans in vitro

Objective To investigate the in vitro antifungal activity of berberine (BBR) in combination with clotrimazole (CLZ) against standard Candida albicans (CA) strain ATCC 10231. Methods The minimum inhibitory concentrations (MIC) of BBR and CLZ alone towards CA-10231 were determined by Kirby-Bauer disk diffusion method. The checkerboard technique was used in the evaluation of the synergistic effect of BBR and CLZ against CA-10231. Fractional inhibitory concentration index (FICI) was employed as the interpretation standard; synergism, FICI≤0.5; indifference, 0.5<FICI≤4; antagonism, FICI>4. Results The averaged MIC of BBR and CLZ alone towards CA-10231 were 32,000 and 32μg/mL respectively. The checkerboard result showed synergy for BBR of averaged MIC 2,000μg/mL (P<0.01) and CLZ of averaged MIC 8μg/mL (P<0.01) with the averaged FICI of 0.3125. Conclusion Both BBR and CLZ inhibit the growth of CA-10231. The results indicate that combination of BBR and CLZ exhibits synergistic effect that is more effective with lower dosage in inhibiting the growth of CA-10231.