Multicenter Comparison of the VITEK 2 Yeast Susceptibility Test with the CLSI Broth Microdilution Reference Method for Testing Fluconazole against Candida spp

Abstract

Standardized broth microdilution (BMD) susceptibility testing of fluconazole against Candida spp. has been available since 1997 (19,21,30). The establishment of a panel of quality control (QC) strains and validated, clinically useful interpretive breakpoints (19, 20,27,30,32) has allowed this method to be used worldwide (3, 6-8, 12, 17, 21, 33).The Clinical and Laboratory Standards Institute (CLSI; formerly National Committee for Clinical Laboratory Standards [NCCLS]) BMD method for testing fluconazole has served as a touchstone for the development of both broth-and agarbased procedures designed to provide simple, flexible, and commercially available alternative susceptibility testing methods for use in the clinical laboratory (8-12, 16, 17, 21, 23-25). The performance of the various commercially available antifungal testing systems has been variable (8,10,16,17), and prior to the present study only two, the Sensititre YeastOne System (Trek, Cleveland, OH) and the Etest (AB BIODISK, Solna Sweden), have been approved by the U.S. Food and Drug Administration (FDA) for in vitro susceptibility testing of fluconazole against Candida spp. (21, 26).Although spectrophotometric reading of BMD MIC endpoints has been shown to be valid and feasible for use in the clinical laboratory (11,12,16, 20,21), this approach has not been incorporated into a commercially available testing method. Recently, bioMerieux (Hazelwood, MO) has developed a yeast susceptibility test that determines growth spectrophotometrically and allows fully automated antifungal susceptibility testing of fluconazole against Candida using the VITEK 2 microbiology system. The fully automated VITEK 2 system allows for the standardization of all of the critical parameters known for antifungal susceptibility testing: inoculum preparation, filling of the device, duration and temperature of incubation, and endpoint determination. The yeast susceptibility test, coupled with the rapid and accurate yeast identification capabilities already available on the VITEK 2 (4), would allow clinical laboratories to perform both yeast identification and antifungal susceptibility testing using a fully automated and completely standardized format. Preliminary studies by Zambardi et al. (G. Zambardi et al., Abstr. 45th Intersci. Conf. Antimicrob. Agents Chemother., abstr. M-1619, 2005 have shown both essential and categorical agreements of Ն90% in a comparison of VITEK 2 MICs with reference BMD MICs for fluconazole and Candida spp. The VITEK 2 results were available in Յ15 h compared to 48 h for the reference BMD method.The purpose of the present study was to validate the performance of the VITEK 2 yeast susceptibility test with fluconazole against a broad range of Candida spp. in three independent laboratories. The VITEK 2 results were compared to those from a frozen reference BMD panel performed according to CLSI guidelines. It is notable that after the completion of the present study the VITEK 2 yeast susceptibility test for fluconazole was approved for clinical use by the U....

A Novel Flucytosine-Resistant Yeast Species, Candida pseudoaaseri, Causes Disease in a Cancer Patient

“…The results for the single antifungal agents were comparable, independent of the system that was used (CLSI reference method, Etest, Vitek 2, or Micronaut). It is known that the Etest correlates well with the CLSI reference method for determining the susceptibility of Candida isolates (3,4,5,11,34) and that the results from the YST card of Vitek 2 have a good correlation with the results from the standard method (9,11,36,37). In contrast to both C. aaseri strains, VK065094…”

Selection of a Surrogate Agent (Fluconazole or Voriconazole) for Initial Susceptibility Testing of Posaconazole against Candida spp.: Results from a Global Antifungal Surveillance Program

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Investigation of Species Distribution and Antifungal Susceptibility of Candida Species Isolated from Various Clinical Samples From Intensive Care Unit Patients

“…Mikrodilüsyon yöntemi antifungal duyarlılık testleri için referans yöntem olarak kabul edilmektedir (20). Ancak çalışmamızda, laboratuvarımızda rutin olarak kullanılan, daha kısa sürede sonuç alınabilmesi ve identifikasyon ve antifungal duyarlılık testlerinin bir arada yapılabilmesi gibi sebeplerle, referans yöntem ile %90'dan fazla uyum gösteren VITEK 2 Compact System sonuçları verilmiştir (21,22). Günümüzde farklı laboratuvarlardan elde edilen değişken sonuçlar nedeniyle antifungal duyarlılık testlerinde, kaspofungin yerine mikafungin veya anidulafungin kullanılmaya başlan-mış olsa da çalışmada otomatize sistemin antifungal duyarlılık panelinde yer alan kaspofungin sonuçları verilmiştir (23).…”