Proposed quality control ranges for 2-microg anidulafungin disk diffusion testing and ability of the method to detect strains with elevated echinocandin MIC values.
Anidulafungin, a newer echinocandin with potent antifungal activity, was tested in an 8-laboratory M23-style quality control (QC) study to determine disk diffusion (DD) method ranges. Two lots of 2-microg disks (MAST and BD) and 3 lots of Mueller-Hinton agar (with 0.5 microg/mL methylene blue + 2% glucose) were used against 4 QC strains. Proposed ranges are Candida albicans ATCC 90028 at 24 to 39 mm (95.0% in range), Candida krusei ATCC 6258 at 20 to 35 mm (94.7%), Candida parapsilosis ATCC 22019 at 15 to 27 mm (95.5%), and Candida tropicalis ATCC 750 at 21 to 38 mm (94.6%); however, the ranges were very wide (13-18 mm), indicating between observer interpretive or reagent variation and compromised reproducibility. Challenge strains with elevated echinocandin MIC values (> or = 4 microg/mL, nonsusceptible) were tested (DD and MIC) and compared with isolates with reproducible anidulafungin MIC results at 2 microg/mL (susceptible). Discrimination between these nonsusceptible and susceptible (MIC, < or = 2 microg/mL) yeast populations was very acceptable, for example, 97.6% categoric agreement by DD method.
Jones
Ronald N
RN
JMI Laboratories, North Liberty, IA 52317, USA.
Ross
James E
JE
Sheehan
Daniel J
DJ
D000077612:Anidulafungin; D000935:Antifungal Agents / Q000494:pharmacology*; D002175:Candida / Q000187:drug effects*; D052978:Disk Diffusion Antimicrobial Tests / Q000379:methods / Q000592:standards*; D054714:Echinocandins / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D011786:Quality Control
D000935:Antifungal Agents; D054714:Echinocandins; D000077612:Anidulafungin