Study objective: The species Candida dubliniensis shares a wide range of phenotypic characteristics with Candida albicans, the most common yeast species isolated from clinical specimens. This is a considerable complication for the detection and identification of Candida dubliniensis from clinical specimens. The lack of data on the incidence of C. dubliniensis in the Czech Republic was the motivation behind the efforts to detect this pathogen in specimens analyzed at the Institute for Microbiology, Faculty of Medicine Masaryk University and St. Anne's Faculty Hospital in Brno. Another aim was to test the reliability of the culture methods used.
Material and methods: Altogether 2260 yeast isolates initially identified as C. albicans were analysed. To differentiate C. dubliniensis from C. albicans, four phenotypic methods were used: colour-based differentiation on CHROMagar Candida medium, culture on medium with 6.5% of NaCl, growth at 42 °C, and colony characteristics on Staib agar. To verify the results, the Bichro-Dubli Fumouze latex agglutination test and species-specific polymerase chain reactions (PCR) were used.
Results: Using phenotypic methods, latex agglutination, and PCR, 50 (2.2%) strains from the study set were assigned to C. dubliniensis. Most (31) C. dubliniensis isolates were recovered from the respiratory tract and the remaining others were three urine isolates, four stool isolates, one central venous catheter isolate, and one blood isolate. With the exception of colour-based differentiation on CHROMagar Candida medium showing a specificity of 85.5%, all the culture methods used have a high sensitivity and a high specificity.
Conclusion: Identification of C. dubliniensis as C. albicans was confirmed in various clinical specimens, most often from the upper respiratory tract. The colour-based differentiation of C. dubliniensis from C. albicans on chromogenic CHROMagar Candida medium can only be recommended as a screening test for the differentiation of C. dubliniensis from other species of the genus Candida. The remaining three methods are highly reliable. The final identification should be based on a combination of these methods, with the species-specific PCR or latex agglutination test used for verification.