[Isolation of Candida dubliniensis in different clinical samples. Analysis of phenotypical methods to differentiate...

In order to estimate the frequence of Candida dubliniensis in clinical samples in F. J. Muñiz Infectious Diseases Hospital, a total of 388 yeasts from September 2005 to August 2007. There were 212 isolates which presented a green color on CHROMagar Candida medium and produced germ tubes and chlamidoconidiae in milk-agar; so as to distinguish whether they corresponded to Candida albicans or C. dubliniensis, different phenotypical methods were utilized. It was also evaluated the usefulness of each one in order to suggest a simple, economic and reliable identification algorithm. Each isolate was subcultured in two chromogenic media and then, the following determinations were done: chlamidospores production in Staib-agar, tomato-carrot-agar and tobacco-agar, colonies macromorphology was also studied in the last medium; opacity-test in Tween 80-CaCl2 agar (lipase activity), growing capacity at 45 degrees C, and D-xylose assimilation. Thirteen strains (6.1%) corresponded to C. dubliniensis. The difference in color between both species on chromogenic media was not so stressed as it is pointed out in some works. The more specific and sensitive tests were the ability to grow at 45 degrees C, D-xylose assimilation, color and macroscopic appearance in tobacco-agar. Between 11.6% and 15.1% of C. albicans strains produced chlamidoconidiae in the 3 differential media tested. The opacity halo (lipase) was evident in 95.6% of C. albicans isolates but 2 out of 13 C. dubliniensis also presented precipitation halo. We consider that at least 3 different phenotypical methods should be used to distinguish properly these two species since none of the tests is absolutely sensitive or specific.