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Journal of Clinical Microbiology, February 2000, p. 537-541, Vol. 38, No. 2
Division of Infectious Diseases, Department
of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical
School, Boston, Massachusetts
Received 16 June 1999/Returned for modification 31 July
1999/Accepted 21 October 1999
This report presents a semisolid agar antifungal susceptibility
(SAAS) method for the rapid susceptibility screening of yeasts and
molds. The reproducibility and accuracy of the SAAS method were
assessed by comparing the MICs of amphotericin B and fluconazole obtained for 10 candidate quality control (QC) American Type Culture Collection yeast strains in
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Copyright © 2000, American Society for Microbiology. All rights reserved.
Preliminary Evaluation of a Semisolid Agar
Antifungal Susceptibility Test for Yeasts and Molds
15 replicates with those found by six
independent laboratories using the National Committee for Clinical
Laboratory Standards (NCCLS) M27-P broth macrodilution method (M. A. Pfaller et al., J. Clin. Microbiol. 33:1104-1107, 1995).
Overall, 96% of MICs for both drugs fell within 1 log2 dilution of the modal MIC for each strain. The MICs for amphotericin B
showed 99% agreement with the NCCLS proposed QC ranges within 1 log2 dilution. Likewise, the MICs for fluconazole at
75%
growth reduction showed 99% agreement for seven strains.
Three strains, Candida albicans ATCC 24333 and ATCC 76615 and Candida tropicalis ATCC 750, showed a less sharp
fluconazole endpoint at
75% growth reduction, but at >50% growth
reduction, the agreement was 98% within 1 log2 dilution of
the proposed range. The MIC agreement within the proposed
range for the suggested QC strains Candida parapsilosis
ATCC 22019 and Candida krusei ATCC 6258 was 100% for
fluconazole and 100% within 1 log2 dilution of the
proposed range for amphotericin B. The SAAS method demonstrated the
susceptibility or resistance of 25 clinical isolates of filamentous
fungi such as Aspergillus fumigatus to amphotericin B,
itraconazole, and fluconazole, usually within 48 h. Although the
results are preliminary, this SAAS method is promising as a rapid and
cost-effective screen and is worthy of concerted investigation.
*
Corresponding author. Present address: Division of
Geographic Medicine and Infectious Diseases, Tufts University School of Medicine, New England Medical Center, Box 041, 750 Washington St.,
Boston, MA 02111. Phone: (617) 636-7010. Fax: (617) 636-8525. E-mail:
shadley{at}lifespan.org.
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