Comparative Evaluation of National Committee for Clinical Laboratory Standards Broth Macrodilution and Agar Dilution Screening Methods for Testing Fluconazole Susceptibility of Cryptococcus neoformans |
| |
| Authors: | William R. Kirkpatrick Robert K. McAtee Sanjay G. Revankar Annette W. Fothergill Dora I. McCarthy Michael G. Rinaldi Thomas F. Patterson |
| |
| Affiliation: | Departments of Medicine1. and Pathology,2. University of Texas Health Science Center at San Antonio, and Audie Murphy Division, South Texas Veterans Health Care System,3. San Antonio, Texas 78284 |
| |
| Abstract: | A simple screening method for fluconazole susceptibility of Cryptococcus neoformans using 2% dextrose Sabouraud dextrose agar (SabDex) with fluconazole was compared to the National Committee for Clinical Laboratory Standards (NCCLS) broth macrodilution method. By this method, fluconazole-susceptible C. neoformans isolates are significantly smaller on medium with fluconazole than on fluconazole-free medium. Isolates with decreased susceptibility have normal-size colonies on medium containing fluconazole. The 48-h NCCLS broth macrodilution MICs (NCCLS MICs) for isolates with normal-size colonies on 8- or 16-μg/ml fluconazole plates were predicted to be ≥8 or ≥16 μg/ml, respectively. On medium with 16 μg of fluconazole per ml, all strains (84 of 84) for which the NCCLS MICs were <16 μg/ml were correctly predicted, as were all isolates (7 of 7) for which the MICs were ≥16 μg/ml. Agar dilution appears to be an effective screening method for fluconazole resistance in C. neoformans. |
| |
| Keywords: | |
|
|
