Evaluation of Etest method for determining fluconazole and voriconazole MICs for 279 clinical isolates of Candida species infrequently isolated from blood

The performance of Etest in fluconazole and voriconazole testing of 279 isolates of uncommon Candida spp. was assessed in comparison with the National Committee for Clinical Laboratory Standards (NCCLS)approved standard broth microdilution (BMD) method. The NCCLS method employed RPMI 1640 broth medium, and MICs were read after incubation for 48 h at 35 C. Etest MICs were determined with RPMI agar containing 2% glucose and were read after incubation for 48 h at 35 C. The isolates include Candida krusei, C. lusitaniae, C. guilliermondii, C. kefyr, C. rugosa, C. lipolytica, C. pelliculosa, C. dubliniensis, C. famata, C. zeylanoides, C. inconspicua, and C. norvegensis. Overall agreement between Etest and BMD MICs was 96% for fluconazole and 95% for voriconazole. Where a discrepancy was observed between Etest and the reference method, the Etest tended to give lower values with both fluconazole and voriconazole. The Etest method using RPMI agar appears to be a useful method for determining fluconazole and voriconazole susceptibilities of uncommon species of Candida.