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.The Etest stable agar gradient MIC method (AB BIODISK, Solna, Sweden) has been shown to be useful in testing Candida spp. against a variety of antifungal agents, including fluconazole and voriconazole (1,3,9,11,12,14,16,17,22,24). The species of Candida tested in these studies generally represent those most commonly isolated from clinical sources and are dominated by Candida albicans, C. glabrata, C. parapsilosis, and C. tropicalis, which account for 95 to 97% of all clinical isolates of Candida spp. (8,13,15,18). Thus, although Etest has been validated for the four most common species of Candida, the evidence supporting its use in testing the less common species is lacking.Among the approximately 17 species of Candida reported to cause bloodstream infections (BSI) (8), 12 or 13 of these species account for less than 5% of all Candida BSI (19). These rare species include among others, C. krusei, C. lusitaniae, C. guilliermondii, C. kefyr, C. rugosa, and C. dubliniensis, several of which may pose problems with antifungal resistance and nosocomial spread (4,5,7,23,26). Although less common than C. albicans, C. glabrata, C. parapsilosis, and C. tropicalis, these species may pose difficult management problems for individual patients, which may benefit from the application of antifungal susceptibility testing (21). Given the use of Etest for antifungal susceptibility testing of the common Candida spp. causing BSI, it is reasonable to validate its use for testing systemically active agents, such as fluconazole and voriconazole, against these less common species as well.The purpose of the present study is to expand the Etest database for fluconazole and voriconazole by testing an international collection of 279 clinical BSI isolates of 12 uncommon species of Candida obtained from 68 different locations in 26 nations. The fluconazole and voriconazole MICs determined by Etest are compared to MICs determined by the National Committee for Clinical Laboratory Standard...

The performance of the Etest for voriconazole and amphotericin B susceptibility testing of 162 isolates of Cryptococcus neoformans was assessed against the National Committee for Clinical Laboratory Standards (NCCLS) broth microdilution method. The NCCLS method employed RPMI 1640 broth medium, and MICs were read after incubation for 72 h at 35°C. MICs were determined by Etest for all 162 isolates with RPMI 1640 agar containing 2% glucose (RPG agar) and were read after incubation for 72 h at 35°C. The Etest results for both voriconazole and amphotericin B correlated well with reference MICs. Agreement was 94% for voriconazole and 99% for amphotericin B. When discrepancy was noted between the results obtained by Etest and broth microdilution for voriconazole, the Etest generally provided a higher MIC. The Etest method using RPG agar appears to be a useful method for determining the susceptibility of C. neoformans to voriconazole and amphotericin B.Numerous studies have shown that when performed according to the manufacturer's instructions, the Etest stable agar gradient method (AB BIODISK, Solna, Sweden) provides excellent performance for testing Candida species against a variety of antifungal agents including polyenes, azoles, echinocandins, and flucytosine (4-6, 12, 13, 15-17, 21, 23). Some studies have also included isolates of Cryptococcus neoformans and have demonstrated the suitability of Etest using RPMI 1640 agar supplemented with 2% glucose (RPG agar) for determining the in vitro susceptibility of this pathogenic yeast to amphotericin B, fluconazole, itraconazole, and flucytosine (1,4,5,8,11,13,21,23). These studies have been limited by the inclusion of low numbers of C. neoformans isolates, and none have included any of the new triazole antifungal agents.Voriconazole is a new triazole with broad-spectrum activity against Candida spp., Aspergillus spp. and other filamentous fungi, and C. neoformans (7,9,14,(18)(19)(20)22). Voriconazole has been tested in vitro against Candida spp. by both the broth microdilution (BMD) method and Etest (15), and voriconazole has been tested against C. neoformans by the BMD method (14). At this time, there are no studies evaluating the performance of Etest with voriconazole against C. neoformans.In this study, we have evaluated the performance of the Etest for voriconazole using RPG by comparing the results with those obtained using the National Committee for Clinical Laboratory Standards (NCCLS) BMD method for testing 162 clinical isolates of C. neoformans. In addition, because a recent report by Aller et al. (1) found a very poor level of agreement between Etest and the BMD method for testing C. neoformans against amphotericin B, we have also included amphotericin B in the evaluation. MATERIALS AND METHODSTest organisms. One hundred sixty-two clinical isolates of C. neoformans were selected for testing. These isolates were all recent clinical isolates from 50 geographically diverse medical centers worldwide. The C. neoformans organisms had all been isolated from either ce...