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Journal of Clinical Microbiology, Nov 1997, 2878-2882, Vol 35, No. 11
CJ Clancy and MH Nguyen
We determined the fluconazole MICs for 101 clinical isolates of Candida and
Cryptococcus neoformans using the macro- and microdilution methods
recommended by the National Committee for Clinical Laboratory Standards. We
compared the MICs obtained by these methods with those obtained by a
photometric assay that quantified the reduction of 3-(4,5-
dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) by viable
fungi. The MIC determined by this method was defined as the highest
fluconazole concentration associated with the first precipitous drop in
optical density. For Candida, both the MTT and the microdilution methods
demonstrated excellent agreement with the standard macrodilution method.
The MTT method, however, generated MICs at 24 h that were comparable to
those generated by the standard macrodilution method, whereas the
microdilution method required 48 h. For C. neoformans, the levels of
agreement between the MICs determined by the MTT and microdilution methods
after 48 h and those determined by the standard 72-h macrodilution method
were 94% (29 of 31) and 94% (29 of 31), respectively. The MTT method
therefore provided results comparable to those of currently recommended
methods and had the advantages of a more rapid turnaround time and
potential adaptability to use as an automated system. Furthermore, the MICs
determined by the MTT method were determined photometrically, thereby
eliminating reader bias.
Copyright © 1997 by the American Society for Microbiology. All rights reserved.
Comparison of a photometric method with standardized methods of antifungal susceptibility testing of yeasts [In Process Citation]
Department of Medicine, College of Medicine, University of Florida, and the Veterans Affairs Medical Center, Gainesville 32610, USA.
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