Interlaboratory comparison of results of susceptibility testing with caspofungin against Candida and Aspergillus species.
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" (MIC(2)) 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. MIC(2) 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.
Odds
Frank C
FC
Aberdeen Fungal Group, University of Aberdeen, Institute of Medical Sciences, Aberdeen AB25 2ZD, United Kingdom. f.odds@abdn.ac.uk
Motyl
Mary
M
Andrade
Roberto
R
Bille
Jacques
J
Cantón
Emilia
E
Cuenca-Estrella
Manuel
M
Davidson
Amanda
A
Durussel
Christian
C
Ellis
David
D
Foraker
Elyse
E
Fothergill
Annette W
AW
Ghannoum
Mahmoud A
MA
Giacobbe
Robert A
RA
Gobernado
Miguel
M
Handke
Rosemary
R
Laverdière
Michel
M
Lee-Yang
Wendy
W
Merz
William G
WG
Ostrosky-Zeichner
Luis
L
Pemán
Javier
J
Perea
Sophia
S
Perfect
John R
JR
Pfaller
Michael A
MA
Proia
Laurie
L
Rex
John H
JH
Rinaldi
Michael G
MG
Rodriguez-Tudela
Juan-Luis
JL
Schell
Wiley A
WA
Shields
Christine
C
Sutton
Deanna A
DA
Verweij
Paul E
PE
Warnock
David W
DW
D000935:Antifungal Agents / Q000494:pharmacology*; D001230:Aspergillus / Q000187:drug effects* / Q000302:isolation & purification; D002175:Candida / Q000187:drug effects* / Q000302:isolation & purification; D000077336:Caspofungin; D054714:Echinocandins; D015725:Fluconazole / Q000494:pharmacology; D005843:Geography; D006801:Humans; D007753:Laboratories / Q000592:standards*; D055666:Lipopeptides; D008826:Microbial Sensitivity Tests / Q000592:standards*; D010455:Peptides / Q000494:pharmacology*; D010456:Peptides, Cyclic; D011786:Quality Control; D015203:Reproducibility of Results
D000935:Antifungal Agents; D054714:Echinocandins; D055666:Lipopeptides; D010455:Peptides; D010456:Peptides, Cyclic; D015725:Fluconazole; D000077336:Caspofungin