Objectives: The European Committee on Antibiotic Susceptibility Testing has developed a proposed standard for AFST of yeasts based on reference procedure of NCCLS M27-A, but incorporating modifications (RPMI-2% glucose, inoculum size of 10 5 CFU/ml, spectrophotometrical reading) in order to get an automated AFST and to shorten from 48h to 24h the incubation period for MIC determination. We have analyzed the correlation between EUCAST procedure, NCCLS micromethod and two commercial methods: Etest and Sensititre-YeastOne. Methods: A total of 60 Candida spp. clinical isolates (10 each C. albicans (CA), C. tropicalis (CT), C. parapsilosis (CP), C. glabrata (CG), C. krusei (CK), C. lusitaniae (CL)) were tested. CK ATCC6258 and CP ATCC22019 were included as QC strains. Triplicate testing on 3 separate days was performed vs. amphotericin B (AB), fluconazole (FLZ), itraconazole (ITZ), ketoconazole (KTZ), voriconazole (VZ), and flucytosine (FC).. Analysis: (i) Agreement (AGR): discrepancies of no more than two 2X dilutions. (ii) Correlation: intraclass correlation coefficient (ICC), over a maximum value of 1. Results: Overall, the AGR and ICC between EUCAST standard and NCCLS method were 97.2% and 0.96, respectively; between EUCAST method and Etest were 91% and 0.89; and between EUCAST standard and Sensititre YeastOne the AGR was 75% and ICC was 0.92. For AB, the correlation between EUCAST and Sensititre method was significantly lower with AGR and ICC values of 50.5% and 0.29, respectively. For azole agents, the correlation between EUCAST and both commercial techniques was high, detecting azole resistant strains. Conclusions: (i) The EUCAST standard and the NCCLS micromethod are comparable for AFST of all antifungal agents and Candida spp. (ii) The correlation between EUCAST method and Etest is high. (iii) EUCAST and Sensititre methods are not comparable for AB. (iii) Etest and Sensititre-YeastOne methods detect azole resistant strains.
Full conference title:
The 15 th Congress of the International Society for Human and Animal Mycology
- ISHAM 15th (2003)