Comparative evaluation of alternative methods for broth dilution susceptibility testing of fluconazole against Candida albicans.
A comparative evaluation of methods for broth macro- and microdilution susceptibility testing of fluconazole was conducted with 119 clinical isolates of Candida albicans. Macro- and microdilution testing were performed according to National Committee for Clinical Laboratory Standards recommendations. For reference macrodilution testing, an 80% inhibition endpoint (MIC 80%) was determined after 48 h of incubation in accordance with National Committee for Clinical Laboratory Standards proposed standard M27-P. Microdilution endpoints were scored as the first tube or well in which a prominent reduction in turbidity (score 2 out of a possible 4) was observed compared with the growth control (Micro MIC-2). Alternative endpoint criteria were assessed independently of the reference MIC 80% and Micro MIC-2 values and included a colorimetric microdilution endpoint determined by using an oxidation-reduction indicator (Alamar Blue; Alamar Bio-sciences Inc., Sacramento, Calif.). The MICs for the two microdilution test systems were read after 24 and 48 h of incubation. The percentage of fluconazole MICs within 2 doubling dilutions of the macrodilution reference values was 94% for both microdilution tests read at 24 h. Agreement was slightly lower at 48 h and ranged from 91 to 93%. Comparison of Micro MIC-2 and colorimetric microdilution MICs resulted in agreements of 97 and 93% at 24 and 48 h, respectively. These results show excellent agreement among alternative methods for fluconazole susceptibility testing.
Pfaller
M A
MA
Department of Pathology, Oregon Health Sciences University, Portland 97201.
Grant
C
C
Morthland
V
V
Rhine-Chalberg
J
J
D002176:Candida albicans / Q000187:drug effects* / Q000302:isolation & purification; D002180:Candidiasis, Oral / Q000188:drug therapy / Q000382:microbiology; D004352:Drug Resistance, Microbial; D005069:Evaluation Studies as Topic; D015725:Fluconazole / Q000494:pharmacology*; D006801:Humans; D008826:Microbial Sensitivity Tests / Q000379:methods* / Q000592:standards; D012015:Reference Standards
D015725:Fluconazole