Susceptibility testing of Prototheca bovis isolates from cases of bovine mastitis using the CLSI reference broth microdilution method and the Sensititre YeastOne colorimetric panel

Abstract

A total of 62 Prototheca bovis isolates from cases of bovine mastitis were tested for susceptibility to different antifungal compounds by the Clinical and Laboratory Standards Institute (CLSI) reference microdilution method and a commercial colorimetric microdilution panel (Sensititre YeastOne). All isolates displayed low susceptibility to echinocandins (MICs > 8 mu g/ml for anidulafungin, caspofungin, and micafungin), flucytosine (MIC > 64 mu g/ml), and the azoles enilconazole and fluconazole (MICs > 4 and > 64 mu g/ml, respectively). Moreover, 45.2, 32.3, and 1.6% of isolates had MICs> 4 mu g/ml for ketoconazole, terbinafine, and voriconazole, respectively, when tested by the CLSI method. In contrast, all isolates were more susceptible to the polyene compounds amphotericin B and nystatin, and itraconazole, posaconazole, and ravuconazole (MICs