Identification of Candida auris by use of the updated vitek 2 yeast identification system, version 8.01: A multilaboratory evaluation study

Abstract

Candida auris is an emerging multidrug-resistant yeast that has been systematically incorrectly identified by phenotypic methods in clinical microbiology laboratories. The Vitek 2 automated identification system (bioMérieux) recently included C. auris in its database (version 8.01). We evaluated the performance of the Vitek 2 YST ID card to identify C. auris and related species. A panel of 44 isolates of Candida species (C. auris, n=35; Candida haemulonii, n=5; Candida duobushaemulonii, n=4) were tested by three different hospital-based microbiology laboratories. Among 35 isolates of C. auris, Vitek 2 yielded correct identification in an average of 52% of tested samples. Low-discrimination (LD) results with an inability to distinguish between C. auris, C. duobushaemulonii, and Candida famata were obtained in an average of 27% of samples. Incorrect identification results were obtained in an average of 21% of samples, the majority (91%) of which were reported as C. duobushaemulonii and the remaining 9% of which were reported as Candida lusitaniae/ C. duobushaemulonii. The proportion of correct identification was not statistically different across different centers (P=0.78). Stratification by genetic clades demonstrated that 100% (n=8) of the strains of the South American clade were correctly identified compared to 7% (n=10) and 0% (n=4) from the African and East Asian clades, respectively. None of the non-auris Candida strains (n=9) were incorrectly identified as C. auris. Our results show that the Vitek 2 (version 8.01) yeast identification system has a limited ability to correctly identify C. auris. These data suggest that an identification result for C. duobushaemulonii should warrant further testing to rule out C. auris. The overall performance of the Vitek 2 seems to differ according to C. auris genetic clade, with the South American isolates yielding the most accurate results.