Evaluation of six commercial systems for identification of medically important yeasts

Abstract

Six commercially available systems for the identification of yeasts were evaluated using 133 clinical isolates and four reference strains that had been previously identified by conventional methods and 19 recent clinical isolates that had been identified by the ID32C system (bioMérieux, France). The total identification rates (TIR) established for the total number of strains tested and the database identification rates (DBIR) established for the strains included in the respective manufacturer databases were both determined. After incubation for 4 h, the TIR and DBIR were 78% and 84%, respectively, for the RapID Yeast Plus system (Innovative Diagnostic Systems, USA). After incubation for 24 h, the TIR and DBIR were 32% and 32%, respectively, for the ID32C, 65% and 67% for the Auxacolor system (Sanofi Diagnostics Pasteur, France), 62% and 65% for the Fungichrom I system (International Microbio, France), 52% and 65% for the Fungifast I twin system (International Microbio), and 62% and 68% for the API Candida system (bioMérieux). The maximum TIR and DBIR (+/- 1%) obtained after incubation for 48 h were 86% and 88% for the Auxacolor, 85% and 89% for the Fungichrom I, 78% and 98% for the Fungifast I twin, and 82% and 91% for the API Candida. For the ID32C, the maximum TIR and DBIR were 98% and 98%, respectively, but these values were obtained only after 72 h of incubation. In addition, the six systems varied in their ease of use and readings. In conclusion, based on results obtained with 156 strains, the Auxacolor and Fungichrom systems seem the most appropriate for use in a clinical microbiology laboratory, due to their ease of use and reading, their rapidity, their cost per test, and their relatively high TIR results, which indicated acceptable performance with strains frequently isolated in our hospital. For a reference identification, the ID32C remains the sole system usable.