Comparative Evaluation of FUNGITEST and Broth Microdilution Methods for Antifungal Drug Susceptibility Testing of Candida Species and Cryptococcus neoformans

The FUNGITEST method (Sanofi Diagnostics Pasteur, Paris, France) is a microplate-based procedure for the breakpoint testing of six antifungal agents (amphotericin B, flucytosine, fluconazole, itraconazole, ketoconazole, and miconazole). We compared the FUNGITEST method with a broth microdilution test, performed according to National Committee for Clinical Laboratory Standards document M27-A guidelines, for determining the in vitro susceptibilities of 180 isolates of Candida spp. (50 C. albicans, 50 C. glabrata, 10 C. kefyr, 20 C. krusei, 10 C. lusitaniae, 20 C. parapsilosis, and 20 C. tropicalis isolates) and 20 isolates of Cryptococcus neoformans. Overall, there was 100% agreement between the methods for amphotericin B, 95% agreement for flucytosine, 84% agreement for miconazole, 83% agreement for itraconazole, 77% agreement for ketoconazole, and 76% agreement for fluconazole. The overall agreement between the methods exceeded 80% for all species tested with the exception of C. glabrata (71% agreement). The poorest agreement between the results for individual agents was seen with C. glabrata (38% for fluconazole, 44% for ketoconazole, and 56% for itraconazole) and C. tropicalis (50% for miconazole). The FUNGITEST method misclassified as susceptible 2 of 12 (16.6%) fluconazole-resistant isolates, 2 of 10 (20%) itraconazole-resistant isolates, and 4 of 8 (50%) ketoconazole-resistant isolates of several Candida spp. Further development of the FUNGITEST procedure will be required before it can be recommended as an alternative method for the susceptibility testing of Candida spp. or C. neoformans.The rising prevalence of serious fungal infections and antifungal drug resistance has created an increased demand for reliable methods of in vitro testing of antifungal agents that can assist in their clinical use. The National Committee for Clinical Laboratory Standards (NCCLS) has developed a standardized broth macrodilution method for the testing of Candida spp. and Cryptococcus neoformans (9). This reference method and microdilution adaptations of it have been reported to give almost identical results (1, 3, 4, 11, 18). However, these methods are time-consuming and labor-intensive and have not eliminated the need for simpler and more economical methods of routine testing.The FUNGITEST method (Sanofi Diagnostics Pasteur, Paris, France) is a commercial procedure for the breakpoint testing of six antifungal drugs (amphotericin B, flucytosine, fluconazole, itraconazole, ketoconazole, and miconazole). Each 16-well microplate contains 2 negative control wells, 2 positive growth control wells, and 12 drug-containing wells. Each drug is provided at two concentrations in dehydrated form and is reconstituted by adding the inoculum suspension in RPMI 1640 medium. The FUNGITEST method is not available in the United States. In this study we compared the FUNGITEST method with a broth microdilution adaptation of the NCCLS reference method using 200 isolates of seven Candida spp. and C. neoformans.(This work was presented in part at the 37th Interscience Conference on Antimicrobial Agents and Chemotherapy, Toronto, Ontario, Canada, 28 September to 1 October 1997.)