P. KASTNER*, C. SAND, R.P. RENNIE, National Centre for Mycology, University of Alberta Hospital, Edmonton, Alberta

Objective: To evaluate the Auxacolor 2 (BioRad) system which is based on the principal of sugar assimilation. This kit was compared to the API 20C AUX (bioMerieux) used in our laboratory for routine assimilation tests.

Methods: A total of 135 strains of Candida species, Cryptococcus species, Geotrichum species, Saccharomyces cerevisiae, and Trichosporon species, in addition to 4 ATCC quality control strains were tested against the Auxacolor 2 and API 20C AUX according to the manufacturers instructions. Inocula for each method were prepared from the same primary culture plates and adjusted to achieve the appropriate CFU/mL. Panels were incubated at 30°C in air and were read after 24, 48 and 72 hrs. of incubation.

Results: The Auxacolor 2 performance with the 135 clinical isolates; 67 (50%) were identified correctly and 9 (6%) were identified incorrectly. Biochemical tests for 35 strains (26%) were considered correct but the correct identification was ruled out based on the complementary criteria. A total of 24 strains (18%) were not identified; biochemical tests did not provide a profile code. For a few strains, the code index had overlapping results with several options (e.g.: C. krusei, C. lipolytica, C. norvegensis). These profiles were difficult to interpret. There were 4 isolates where the results reverted (at 24/48 hr. the result was pos. and at 72 hr the result was neg.).

Conclusion: The Auxacolor 2 is easy to use and interpret. This system could be used for initial screening in a laboratory that has limited resources, but may provide confusing results. Further identification of yeasts requires more extensive testing for complete identification.