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 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-microg/ml fluconazole plates were predicted to be > or =8 or > or =16 microg/ml, respectively. On medium with 16 microg of fluconazole per ml, all strains (84 of 84) for which the NCCLS MICs were <16 microg/ml were correctly predicted, as were all isolates (7 of 7) for which the MICs were > or =16 microg/ml. Agar dilution appears to be an effective screening method for fluconazole resistance in C. neoformans.
Kirkpatrick
W R
WR
Department of Medicine, University of Texas Health Science Center at San Antonio, 78284-7881, USA.
McAtee
R K
RK
Revankar
S G
SG
Fothergill
A W
AW
McCarthy
D I
DI
Rinaldi
M G
MG
Patterson
T F
TF
D000935:Antifungal Agents / Q000494:pharmacology*; D003455:Cryptococcus neoformans / Q000187:drug effects*; D003470:Culture Media / Q000494:pharmacology; D005069:Evaluation Studies as Topic; D015725:Fluconazole / Q000494:pharmacology*; D006801:Humans; D008826:Microbial Sensitivity Tests / Q000592:standards
D000935:Antifungal Agents; D003470:Culture Media; D015725:Fluconazole