Evaluation of CHROMagar Candida, VITEK2 YST and VITEK® MS for identification of Candida strains isolated from blood cultures

C is an increasingly common problem in hospitalized patients, especially among immunocompromised patients. C. albicans is the predominant cause of candidemia, with a crude mortality rate of approximately 40% [1-5]. However, non-albicans Candida species such as C. parapsilosis, C. glabrata, C. krusei and C. tropicalis are emerging as opportunistic pathogens [2]. C. parapsilosis is the second most frequently isolated Candida species from blood cultures in Europe, Latin America and Canada [2-6]. Non-albicans Candida species have decreased susceptibility to antifungal agents [2]. For this reason, fast accurate diagnosis and treatment are very important for the prognosis of patients with candidemia [6]. Several phenotypic tests based on colony morphology have been developed to distinguish Candida strains. In clinical laboratories, these methods are used as reference identification procedures [7, 8]. However, phenotypic tests are not practical for the clinical laboratory because they are timeconsuming and labor-intensive. Therefore, Vitek 2 YST card automated systems and chromogenic media for the identification of Candida species have been developed [8-17]. MALDI-TOF MS technology was seen as a revolution in microbiology laboratories for the identification of Candida species [18-23]. CHROMagar Candida (Oxoid BrillianceTM Candida agar, England) is based on the formation of various colored colonies which result from the use of chromogenic substrates by species specific enzymes. These enzymes allow organisms to be identified at species level by their color and colony characteristics [8]. This media has been used to identify Candida spp. in several studies. Most studies related to this medium were carried out with stock isolates and direct clinical specimens [9-13]. In these studies, the percentage of correct identification by using CHROMagar Candida were reported as 99.4-95% [10, 11, 13]. The VITEK2 YST system (bioMérieux, France) is a fully automated instrument for the identification and susceptibility testing of microorganisms [14]. The ID-YST database of VITEK2 YST for yeast identification comprises 54 different taxa, including newly described species and takes into account recent advances in taxonomy. The time to identification by the VITEK2 YST system was 18 hours, compared to 48 to 72 hours by the API 20C AUX method [15]. Matrix-assisted laser desorption ionisation time of flight mass spectrometry (MALDI-TOF MS) is based on the detection of specific proteins released from microbial cell’s surface and has also Evaluation of CHROMagar Candida, VITEK2 YST and VITEK® MS for identification of Candida strains isolated from blood cultures