Interlaboratory comparison of results of susceptibility testing with caspofungin against candida and aspergillus species
Date
2004
Authors
Odds, F.
Motyl, M.
Andrade, R.
Bille, J.
Canton, E.
Cuenca-Estrella, M.
Davidson, A.
Durussel, C.
Ellis, D.
Foraker, E.
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Journal article
Citation
Journal of Clinical Microbiology, 2004; 42(8):3475-3482
Statement of Responsibility
Frank C. Odds, Mary Motyl, Roberto Andrade, Jacques Bille, Emilia Cantón, Manuel Cuenca-Estrella, Amanda Davidson, Christian Durussel, David Ellis, Elyse Foraker, Mahmoud A. Ghannoum, Robert A. Giacobbe, Miguel Gobernado, Rosemary Handke, Michel Laverdière, Wendy Lee-Yang, William G. Merz, Luis Ostrosky-Zeichner, Javier Pemán, Sophia Perea, John R. Perfect, Michael A. Pfaller, Laurie Proia, John H. Rex, Michael G. Rinaldi, Juan-Luis Rodriguez-Tudela, Wiley A. Schell, Christine Shields, Deanna A. Sutton, Paul E. Verweij, and David W. Warnock
Conference Name
Abstract
Seventeen laboratories participated in a study of interlaboratory reproducibility with caspofungin microdilution susceptibility testing against panels comprising 30 isolates of Candida spp. and 20 isolates of Aspergillus spp. The laboratories used materials supplied from a single source to determine the influence of growth medium (RPMI 1640 with or without glucose additions and antibiotic medium 3 [AM3]), the same incubation times (24 h and 48 h), and the same end point definition (partial or complete inhibition of growth) for the MIC of caspofungin. All tests were run in duplicate, and end points were determined both spectrophotometrically and visually. The results from almost all of the laboratories for quality control and reference Candida and Aspergillus isolates tested with fluconazole and itraconazole matched the NCCLS published values. However, considerable interlaboratory variability was seen in the results of the caspofungin tests. For Candida spp. the most consistent MIC data were generated with visual “prominent growth reduction” (MIC2) end points measured at 24 h in RPMI 1640, where 73.3% of results for the 30 isolates tested fell within a mode ± one dilution range across all 17 laboratories. MIC2 at 24 h in RPMI 1640 or AM3 also gave the best interlaboratory separation of Candida isolates of known high and low susceptibility to caspofungin. Reproducibility of MIC data was problematic for caspofungin tests with Aspergillus spp. under all conditions, but the minimal effective concentration end point, defined as the lowest caspofungin concentration yielding conspicuously aberrant hyphal growth, gave excellent reproducibility for data from 14 of the 17 participating laboratories.
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Copyright © 2004 by the American Society for Microbiology.