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Journal of Clinical Microbiology, May 1995, 1094-1097, Vol 33, No. 5
MA Pfaller, SA Messer and S Coffmann
A study to compare three different methods for reading MIC endpoints tested
by the broth microdilution modification of the National Committee for
Clinical Laboratory Standards (Villanova, Pa.) reference method was
conducted. MICs of amphotericin B, flucytosine, fluconazole, itraconazole,
and a new triazole, D0870, were determined for five reference yeast strains
and 100 clinical isolates of Candida spp. MICs were read visually according
to National Committee for Clinical Laboratory Standards guidelines from
microdilution trays that had been (VS) and had not been (V) shaken. MICs
were also determined spectrophotometrically (SP) at 492 nm. SP endpoints
were determined as the concentrations resulting in a > or = 50%
inhibition of growth (flucytosine and azoles) and a > or = 90%
inhibition of growth (amphotericin B) relative to control growth. The five
reference strains were tested nine times each against all five antifungal
agents, and the MIC results for each reading method were compared with a
3-log2 dilution reference range determined by the macrodilution (M27-P)
method. Overall, 84 to 100% of the MICs determined by V, 93 to 100% of
those determined by VS, and 89 to 100% of those determined by SP fell
within the 3-log2 dilution reference range for each reference strain and
antifungal agent. Reproducibility was 99% for V and SP and 98% for VS.
Agreement among the three methods of reading ranged from 97 to 99%.
Excellent agreement among reading methods was also observed for all
antifungal agents when tested against 100 clinical isolates.(ABSTRACT
TRUNCATED AT 250 WORDS)
Copyright © 1995 by the American Society for Microbiology. All rights reserved.
Comparison of visual and spectrophotometric methods of MIC endpoint determinations by using broth microdilution methods to test five antifungal agents, including the new triazole D0870
Department of Pathology, University of Iowa College of Medicine, Iowa City 52242, USA.
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