Comparison of broth microdilution and Etest® methods for susceptibility testing of amphotericin B in Candida auris.

Amphotericin B remains an important treatment for multidrug-resistant Candida auris. Antifungal susceptibility testing of amphotericin B in C. auris can vary depending on the methodology used. Here, we compared the Etest method and the Clinical and Laboratory Standards Institute broth microdilution reference method for amphotericin B against 60 clinical C. auris isolates from the four major clades. The minimum inhibitory concentrations differed significantly by method (P-value, <.0001), and discrepancies were observed in the interpretation of resistance (categorical agreement, 88.3%; very major error, 33.3%). Broth microdilution may represent a more conservative approach for detecting amphotericin B resistance in C. auris.