Evaluation of disk diffusion method compared to broth microdilution for antifungal susceptibility testing of 3 echinocandins against Aspergillus spp.

We tested the susceptibility of caspofungin, micafungin, and anidulafungin against Aspergillus spp. isolates by the new Clinical and Laboratory Standards Institute M51-A disk diffusion (DD) and the broth microdilution methods. A total of 65 clinical isolates of Aspergillus spp. were evaluated. The DD assay was performed on nonsupplemented Mueller-Hinton agar using caspofungin 2-mu g, micafungin 1-mu g, and anidulafungin 2-mu g disks. Echinocandin minimal effective concentrations (MECs) and inhibition zones (IZs) were read after 24 to 48 (A. terreus) h at 35 degrees C. Caspofungin MECs for all Aspergillus spp. strains tested were <= 0.25 mu g/mL; IZs were >= 15 mm for most species except for A. terreus (11-22 mm). Both micafungin and anidulafungin MECs were <= 0.015 mu g/mL, but micafungin IZs were >= 14 mm while anidulafungin IZs were >= 22 mm. As for caspofungin, the DD method could be a useful method for susceptibility testing of micafungin and anidulafungin against Aspergillus spp. Crown Copyright (C) 2012 Published by Elsevier Inc. All rights reserved.