COMPARATIVE-EVALUATION OF NATIONAL COMMITTEE FOR CLINICAL LABORATORY STANDARDS BROTH MACRODILUTION AND AGAR DILUTION SCREENING METHODS FOR TESTING FLUCONAZOLE SUSCEPTIBILITY OF CRYPTOCOCCUS-NEOFORMANS

A simple screening method for fluconazole susceptibility of Cryptococc us neoformans using 2% dextrose Sabouraud dextrose agar (SabDex) with fluconazole was compared to the National Committee for Clinical Labora tory Standards (NCCLS) broth macrodilution method. By this method, flu conazole-susceptible C. neoformans isolates are significantly smaller on medium dth fluconazole than on fluconazole-free medium. Isolates wi th decreased susceptibility hale normal-size colonies on medium contai ning fuconazole. The 48-h NCCLS broth macrodilution MICs (NCCLS MICs) for isolates with normal-size colonies on 8- or 16-mu g/ml fluconazole plates were predicted to be greater than or equal to 8 or greater tha n or equal to 16-mu g/ml, respectively. On medium with 16 mu g of fluc onazole per ml, all strains (84 of 84) for which the NCCLS MICs were < 16 mu g/ml were correctly predicted, as were all isolates (7 of 7) for which the MICs were greater than or equal to 16 mu g/ml. Agar dilutio n appears to he an effective screening method for fluconazole resistan ce in C. neoformans.