Antifungal activity of anti-fungi drugs against filamentous fungi in vitro

Abstract

Objective To investigate antifungal activities of AMB, ICZ, VRC, CBF against 72 strains of filamentous fungi in vitro. Methods Based on CLSI M38-P and M38-A scheme, MIC of antifungal drugs were determined. The growing inhibitory concentration of 100%, 100%,≥80%, for AMB, VRC ,ICZ act as respective MIC. For caspofungin, the minimal effective concentration (MEC) was determined as the lowest drug concentration showing morphology change of filaments. The fractional inhibitory concentration (FIC) was used to evaluate the effect of combination therapy. FIC was calculated by the following equation: FIC = MIC_(combination)/MIC_(A drug alone) + MIC_(combination)/MIC_(B drug alone). Results MIC90 of AMB, ICZ, CBF, VRC against 72 isolates of filamentous fungi were 8 μg/ml, 4 μg/ml, 2 μg/ml, 8 μg/ml, respectively. MICs range of combined AMB + ICZ, AMB + VRC, ICZ + VRC were 0. 125-16. 97, 0. 2452-1.25, and 0.0625-8. 25 μg/ml respectively. The percent of synergistic interaction of AMB + VRC against filamentous fungi (20.0%-88.9% ) was higher than those of AMB + ICZ ( 10.0% -62.5% ) and ICZ + VRC ( 20.0% - 44.4% ) ( P=0.007 <0.05 ). Conclusions The antifungal activities of four kinds antifungal drugs against 72 strains of filamentous fungi vary in vitro. The therapy of AMB combined with VRC is maybe better than AMB + ICZ and ICZ + VRC for severe fungi infection. Key words: Fungi; Antifungal agents; Microbial susceptibility tests; Drug therapy, combination