COMPARISON OF UPDATED VITEK YEAST BIOCHEMICAL CARD AND API 20C YEAST IDENTIFICATION SYSTEMS

The updated Vitek Yeast Biochemical Card (YBC) was compared with the A PI 20C by using 409 germ tube-negative yeasts and Geotrichum spp. that were either clinical or proficiency sample isolates. The API 20C was the reference standard. The 409 isolates represented nine genera and 2 1 species. Morphology agars were inoculated and interpreted for each i solate. The API 20C identified 406 isolates (99.3%), while the Vitck Y BC identified 367 (89.7%). Both systems identified the majority of yea sts after 24 h of incubation-73.4% were identified by the API 20C and 77.4% were identified by the Vitek YBC. The Vitek 24-11 readings had s ome incorrect identifications. These included 14 isolates of Candida t ropicalis that were identified as Candida parapsilosis (91 to 97% reli ability) and 3 isolates of Candida krusei that were called Blastoschiz omyces capitatus (Geotrichum capitatum), Candida rugosa, and Candida z eylanoides. In total, the Vitek YBC misidentified 30 isolates, while t he API 20C misidentified 3 isolates. In addition, results for 14 isola tes with the Vitek YBC were listed under the category ''no identificat ion.'' Morphology agars were required for identification with 89 isola tes (21.9%) when the API 20C was used and with 50 isolates (12.6%) whe n the Vitek YBC was used. Apart from the price of the Vitek instrument . the API 20C costs $1.28 more per test than the Vitek YBC. Overall, t he updated Vitek YBC compares favorably with the API 20C in the identi fication of common yeasts such as Torulopsis glabrata, C. parapsilosis , and Cryptococcus neoformans. However, problems were encountered with the Vitek system in the identification of C. tropicalis, C. krusei, T ricilosporon spp., and some CrEptococcns spp. The routine use of morph ology agars with either method is recommended.