A comparison of methods for yeast identification including CHROMagar Candida, Vitek system YBC and a traditional biochemical method

Background. CHROMagar Candida (CAC) is a new chromogenic medium for the presumptive identification of clinically-important yeast isolates. A yeast biochemical card (YBC), a part of the Vitek system is an automatic method for the identification of clinically-important yeast isolates. We conducted a comparison of these two methods with a traditional biochemical method in order to choose a rapid and accurate technique for yeast identification. Methods. All yeast isolates were inoculated onto Sabourand dextrose agar (SDA) and CAC, and incubated at 30 °C for 48 hours. All isolates were simultaneously tested using traditional biochemical methods and the yeast biochemical card from the Vitek system. Results. We evaluated 235 yeast isolates from clinical specimens, including 89 Candida albicans, 47 Candida tropicalis, 43 Candida glabrata, six Trichosporon beigelii, and five Candida krusei in addition to 45 isolates of other yeast species. Isolates were presumptively identified on the basis of colony color and appearance on CAC medium. These observations were compared with a traditional biochemical yeast-identification method and also with YBC from the Vitek system. For five commonly-isolated species (Candida albicans, Candida tropicalis, Candida glabrata, Candida krusei and Trichosporon beigelii), agreement among the CAC medium, YBC method and traditional biochemical method were 98.9% (187/189), 96.3% (182/189), 100% (189/189), respectively. Conclusions. From our comparison, the CAC medium is a convenient and economic method to identify five commonly-noted yeast species, and the YBC method warrants a greater cost and requires a longer period of time to obtain reliable results.