[In vitro antifungal susceptibility of dematiaceous filamentous fungi using the E-test]

Abstract

The usefulness of the E-test((R) )has been studied to determine the in vitro susceptibility of 52 isolates of 17 species to five antifungal drugs: amphotericin B, 5-flucytosine, ketoconazole, itraconazole and fluconazole. Minimal inhibitory concentrations were determined following the manufacturers' instructions, except in the preparation of the inoculum. In this case a spectrophotometric method was used to obtain 1-5 ' 10(6) CFU/ml. Two different culture media were included: casitone-agar and RPMI 1640 agar. Most isolates showed clear growth in both media after 96 h of incubation at 37 degrees C. The species showed low MIC concentrations to ketoconazole and itraconazole. Only 55.8% of isolates showed MICs </= 2 mg/l to amphotericin B and 98% of strains presented MICs of 32 mg/l for 5-flucytosine. With the exception of one isolate, the remaining were resistant to fluconazole with MIC values 256 mg/l. No differences were found between the MICs for the two media, but values were easier to read in casitone-agar. These results suggest that itraconazole and ketoconazole should be the antifungals of first choice for treating infections due to the evaluated species. This study showed that the E-test((R) )appears to be a suitable method for testing the susceptibility of dematiaceous filamentous fungi to antifungals.