Comparision of different interpretation criterions of fractional inhibitory concentration for evaluating the in vitro combined effect of antifungal agents

Abstract

Abstract:

Objective To determine the interaction pattern of ketoconazole combined with terbinafine or naftifine, and to evaluate the effects of different interpretation criterions of fractional inhibitory concentration index (FICI) for the in vitro combined effect of antifungal drugs.Methods According to CLSI M38-A2 and M27-A3, a checkerboard broth microdilution method was performed to investigate the in vitro activities of ketoconazole in combination with terbinafine or naftifine against 100 clinical strains isolated from patients with mycosis, including dermatophyte, Candida and Malassezia.Different criterion for the interpretation of fractional inhibitory concentration were employed to evaluate the in vitro combined effect of ketoconazole in combination with terbinafine or naftifine.Standard A:synergy is defined by FICI ≤0.5, antagonism by FICI>4, and no interaction by FICI>0.5, but ≤4;Standard B:synergy is defined by FICI ≤0.5, additive by FICI>0.5, but ≤1, no interaction by FICI>1, but ≤2, and antagonism by FICI>2;Standard C:synergy is defined by FICI ≤1, additive by FICI=1, no interaction by FICI>1, but ≤2, and antagonism by FICI>2.Results Standard A had good consistency with Standard B, Standard C is relatively lenient.According to Standard C, the interpretation might significantly expand the range of synergy.Conclusions The interpretation criterion of fractional inhibitory concentration (Synergy is defined by FICI ≤0.5, antagonism by FICI>4, and no interaction by FICI>0.5, but ≤4) has the advantage of simplicity, convenience and good consistence, and it is worthy of clinical application.

Key words: antifungal agents, combination, susceptibility testing, fractional inhibitory concentration

CLC Number:

R978.5

WU Wei-wei, WANG Qian, GONG Jie, WAN Zhe, WANG Ai-ping, LI Ruo-yu. Comparision of different interpretation criterions of fractional inhibitory concentration for evaluating the in vitro combined effect of antifungal agents[J]. Chinese Journal of Mycology, 2016, 11(2): 85-89.

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