The use of Niger seed agar to screen for Candida dubliniensis in the clinical microbiology laboratory.
Candida dubliniensis is a recently described pathogenic yeast that is closely related to C. albicans. The germ tube test is used routinely in diagnostic laboratories for the identification of C. albicans, and C. dubliniensis may also produce germ tubes under the same conditions. We evaluated a previously described method for differentiating between the two species using Niger seed agar (Staib agar). The aim was to find a useful, user-friendly and cost-effective method for use in diagnostic work. C. albicans produces only yeast cells on this medium after 24 h at 37 degrees C, while C. dubliniensis produces extensive hyphal and pseudohyphal growth that is easily observed. Of 495 yeasts isolated in, or sent for identification to, a diagnostic mycology laboratory 9 isolates (1.8%) were found to be C. dubliniensis. The method was found to be valuable for screening yeasts before proceeding to further identification if positive for hyphal/pseudohyphal growth on Niger seed agar. This method is therefore suitable for the screening of selected yeast isolates in order to identity C. dubliniensis and will further our understanding of the clinical importance of this species.
Mycology Reference Centre, General Infirmary at Leeds, Leeds LS1 3EX, UK. micrb@leeds.ac.uk
Eileen
E
Lees
Richard C
RC
Barton
D000362:Agar; D002175:Candida / Q000145:classification* / Q000302:isolation & purification; D002176:Candida albicans / Q000302:isolation & purification; D017077:Culture Media, Conditioned; D006801:Humans; D007753:Laboratories; D016533:Mycological Typing Techniques / Q000379:methods*; D010936:Plant Extracts; D012639:Seeds / Q000737:chemistry*; D012680:Sensitivity and Specificity
D017077:Culture Media, Conditioned; D010936:Plant Extracts; D000362:Agar