A Novel Selective Medium for Isolation of Candida dubliniensis

Abstract

Candida dubliniensis was first isolated from the oral cavity of AIDS patients as an emerging pathogen. As C. dubliniensis is very closely related to Candida albicans, it is difficult to separate these species from individual clinical samples. Differences in the expression of putative virulence factors and in antifungal susceptibility among different Candida species have raised the need for species-level identification. A novel selective medium for distinguishing C. dubliniensis from C. albicans was developed on the basis of susceptibility to micafungin. The minimum inhibitory concentrations of micafungin were more than 16 μg/ml for C. dubliniensis and less than 0.015 μg/ml for C. albicans. C. dubliniensis grew well, and the average growth recovery of the strains on the selective medium was 66.0% (23.9-97.7%). However, C. albicans did not grow on the medium. Even when C. dubliniensis was treated with saliva, no effects were observed on the growth recovery on the medium. In clinical samples from oral cavity, C. dubliniensis was detected from 3 of 13 denture-wearing subjects using the selective medium. When C. dubliniensis was detected in these 3 subjects, C. albicans always coexisted in the samples. In this study, new selective medium was suggested to be useful for the isolation of C. dubliniensis from oral cavity in clinical samples.