| Abstract: | Infections due to Candida spp. are frequent, particularly in immunocompromised and intensive care unit patients. Antifungal susceptibility tests are now required to optimize antifungal treatment given the emergence of acquired antifungal resistance in some Candida species. An antifungal susceptibility automated method, the Vitek 2 system (VK2), was evaluated. VK2 was compared to the CLSI broth microdilution reference method and the Etest procedure. For this purpose, 205 clinical isolates of Candida spp., including 11 different species, were tested for fluconazole, voriconazole, and amphotericin B susceptibility. For azoles, essential agreement ranged from 25% to 100%, depending on the method used and the Candida species tested. Categorical agreements for all of the species averaged 92.2% and ranged from 14.3 to 100%, depending on the 24-h or 48-h MIC reading by the Etest and CLSI methods and on the Candida species. Results obtained for Candida albicans showed excellent categorical and essential agreements with the two comparative methods. For Candida glabrata, the essential agreement was high with the CLSI method but low with the Etest method, and several very major errors in interpretation were observed between VK2 and the Etest method for both azoles. Low MICs of fluconazole were obtained for all of the Candida krusei isolates, but the VK2 expert software corrected all of the results obtained to resistant. Amphotericin B results showed MICs of ≤1 mg/liter for 201 (VK2), 190 (CLSI), and 202 (Etest) isolates. The AST-YS01 Vitek 2 card system (bioMérieux) is a reliable and practical standardized automated antifungal susceptibility test. Nevertheless, more assays are needed to better evaluate C. glabrata fluconazole sensitivity.Invasive candidiasis infections are of increasing concern, particularly in immunodeficient or intensive care unit patients. The emergence of antifungal resistance and the development of new echinocandin class and broad-spectrum azole fungal agents have complicated the choice of antifungal treatment for candidiasis.Antifungal choice is first based on Candida species identification, but antifungal susceptibility testing will play an increasingly important role when selecting which antifungal drug to use (3). Standardized methods for antifungal susceptibility testing have been available for many years. The Clinical and Laboratory Standards Institute (CLSI) standardized broth microdilution method remains a reference for antifungal susceptibility testing (4). Indeed, clinically relevant interpretative breakpoints are available and quality control strains are validated (11). Nevertheless, this method is complex and laborious to use as a routine method. Alternative, standardized and reliable methods adapted to hospital laboratories, such as the Etest, are now commonly used (2).The objective of this study was to evaluate and compare a new automated antifungal susceptibility test system (AST-YS01 Vitek 2 cards; bioMérieux) to both the CLSI reference broth microdilution method and Etest procedures. For this purpose, 208 clinical isolates of Candida spp. isolated primarily from patients with invasive candidiasis were tested with fluconazole, voriconazole, and amphotericin B.(Preliminary data were presented at the 19th European Congress of Clinical Microbiology and Infectious Diseases, Helsinki, Finland, 16 to 19 May 2009, abstr. P1306.) |
