Differentiation of Candida dubliniensis from Candida albicans on Staib agar and caffeic acid-ferric citrate agar

The methods currently available for the identification of the pathogenic ye ast Candida dubliniensis all have disadvantages in that they are time-consu ming, expensive, and/or, in some cases, unreliable. In a recent study (P. S taib and J. Morschhauser, Mycoses 42:521-524; 1999) of 14 C. dubliniensis a nd II C. albicans isolates, it was suggested that. the ability of C. dublin iensis to produce rough colonies and chlamydospores (chlamydoconidia) on St aib agar (SA) provided a simple means of differentiating it from its close relative C. albicans, Tn the present investigation, we examined the colony morphology and chlamydospore production of 130 C. dubliniensis and 166 C. a lbicans isolates on SA and on the related defined medium caffeic acid-ferri c citrate agar (CAF). All of the C. dubliniensis and C. albicans isolates p roduced chlamydospores on the control medium, i.e., rice-agar-Tween agar. H owever, while none of the C, albicans isolates produced chlamydospores on e ither SA or CAF, 85.4 and 83.8% of the C. dubliniensis isolates produced ch lamydospores on SA and CAF, respectively. All of the C. albicans isolates g rew as smooth, shiny colonies on SA after 48 to 72 h of incubation at 30 de greesC, while 97.7% of the C. dubliniensis isolates grew as rough colonies, many (65%) with a hyphal fringe. In contrast, 87.4% of the C. albicans and 93.8% of the C. dubliniensis isolates yielded rough colonies on CAF. Altho ugh the results of this study confirm that SA is a good medium for distingu ishing between C. dubliniensis and C. albicans, we believe that discriminat ion between these two species is best achieved on the basis of colony morph ology rather than chlamydospore production.