Comparison of susceptibility patterns using commercially available susceptibility testing methods performed on prevalent Candida spp.

The rising rates of invasive fungal infections caused by non-albicans Candida and the increasing emergence of antifungal resistance complicate the management of invasive candidiasis. Accurate and timely antifungal susceptibility testing is critical to targeting antifungal therapy. The purpose of this study was to compare commercially available susceptibility testing methods using prospectively collected Candida isolates. Susceptibility testing was performed on 74 Candida isolates collected from July 2014 to March 2015 using broth microdilution according to the Clinical and Laboratory Standards Institute method, Etest, Vitek 2 (YS-05) and Sensititre. Essential agreement and categorical agreement (CA) were assessed using the reference method. Of the 34 total blood isolates collected, Candida albicans comprised only 38 % (13) of the Candida spp. with Candidaglabrata being nearly as prevalent (29 %, 10). CA using Etest was 86 % for fluconazole, 72 % for caspofungin, 98 % for micafungin and 97 % for anidulafungin. Vitek 2 CA was 90 % for fluconazole and 98 % for caspofungin. Sensititre CA was 93 % for fluconazole, 98 % for caspofungin, 98 % for micafungin and 100 % for anidulafungin. Although our study tested a small population of Candida isolates, our results were variable by method. When implementing antifungal susceptibility testing, clinicians should be aware of the strengths and limitations of each testing method.