Interlaboratory evaluation of the Etest® for antifungal susceptibility testing of dermatophytes

Abstract

A three-site interlaboratory reproducibility evaluation of the Etest® concentration gradient strip method for testing antifungal susceptibilities was conducted using 30 strains of dermatophytes exposed to strips loaded with ketoconazole (KTZ), itraconazole (ITZ), amphotericin B (AMB) and fluconazole (FCZ). Etest® minimal inhibitory concentrations were compared with those obtained using a broth microdilution method. All isolates produced clearly detectable growth at 28°C within 72-96 h for reading with the Etest® method. The highest interlaboratory agreement between Etest® and the microdilution method was shown with FCZ (94%), and the lowest was seen with KTZ (60%). Overall, agreement between the Etest® and microdilution method was variable. It was excellent for AMB (97%), good for ITZ (80%) and KTZ (77%), and low for fluconazole (27%). © 2003 ISHAM.