Comparison of Phenotypic Methods for the Identification of Candida dubliniensis

Background/Purpose Mixed infections caused by different Candida species are the rule rather than the exception. The discrimination between the two closely related species Candida albicans and Candida dubliniensis is not trivial. Therefore, there is a need for fast, reliable, and inexpensive methods with high specificity for the identification and differentiation of these two Candida species, which are frequently detected in the oral cavities of patients with a human immunodeficiency virus infection. Methods We applied several phenotypic identification methods (growth on Rice-agar, Bird-seed agar, CHROMagar® Candida, API ID 32C; growth at 42°C and 45°C) and compared them with genotyping by arbitrarily primed-polymerase chain reaction. Results A sensitivity of 44% for the identification of C. dubliniensis was achieved for growth on Rice-agar, 97% for discrimination on Bird-seed agar, 95% with the assimilation profile index API ID 32C, and 97% when grown at 45°C. We found two API codes not described for C. dubliniensis so far. Additionally, 88% of our C. dubliniensis isolates assimilated palatinose, in contrast to the 1% described in the API reference manual. Conclusion According to our results, cultivation of Candida isolates on Bird-seed agar after screening on CHROMagar® Candida is a very sensitive, simple, and cost-effective method for discriminating C. dubliniensis from C. albicans in routine practice.