Comparison of the Sensititre YeastOne colorimetric method with the NCCLS broth microdilution modified reference method for amphotericin B, fluconazole, itraconazole and voriconazole susceptibility testing against Candida non-albicans species

Objective. A comparative evaluation of the commercial Sensititre YeastOne colorimetric method with an adapted NCCLS M27-A reference microdilution method was performed for antifungal susceptibility testing of 92 non-albicans yeast isolates of the BCCM/IHEM collection against amphotericin B, fluconazole, itraconazole and voriconazole. Material and methods. The following clinical blood isolates were tested: 47 Candida glabrata, 25 Candida parapsilosis, 6 Candida tropicalis, 4 Candida krusei, 1 Candida guilliermondii. 2 Candida lusitaniae, 3 Pichia anomala and 4 Saccharomyces cerevisiae. The Sensititre YeastOne panel was performed according to the manufacturer's instructions. For this colorimetric method, MICs (minimum inhibitory concentration) were determined visually after 24 hours. For the NCCLS reference method, MICs were read spectrophotometrically after 48 hours of incubation. Results and conclusion. The overall agreement within 2 dilutions (MIC+/-1 dilution) by both methods was calculated against the four antifungal agents. This agreement was 72.8, 85.9, 59.8 and 74.4% for amphotericin B, fluconazole, itraconazole and voriconazole, respectively. The main discrepancy between the YeastOne and the NCCLS microdilution method consisted of higher itraconazole MICs for Candida glabrata species, observed with the YeastOne method. For all the tested isolates, no major differences regarding susceptibility categories, were observed. This study demonstrates that YeastOne method can be a useful method for antifungal susceptibility testing in routine clinical laboratories.