Submitted to: Journal of Clinical Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/17/2001
Publication Date: N/A
Interpretive Summary: Certain yeasts cause disease in humans and among them is Candida albicans, which is responsible for the majority of all fungal infections worldwide. Identification of pathogenic yeasts is essential for treatment, but C. albicans and the closely related species C. dubliniensis are often confused with each other and with certain other yeasts. A gene sequence database developed at NCAUR allows identification of all known yeasts. This database was used to produce diagnostic probes for C. albicans and C. dubliniensis to allow rapid detection of these two species in clinical labs.
Technical Abstract: The recent discovery of Candida dubliniensis as a separate species that traditionally has been identified as Candida albicans has led to the development of a variety of biochemical and molecular methods for the differentiation of these two pathogenic yeasts. Ribosomal RNA (rRNA) sequences are well-established phylogenetic markers and probes targeting species-specific rRNA sequences have been used in diagnostic assays for detection and identification of microorganisms. Peptide nucleic acid (PNA) is a DNA mimic with improved hybridization characteristics and the neutral backbone of PNA probes offer significant advantages in whole cell in situ hybridization assays. In this study, we developed PNA probes targeting the rRNA of C. albicans and C. dubliniensis and applied them to a fluorescence in situ hybridization method (PNA FISH) for differentiation between C. albicans and C. dubliniensis. Liquid cultures were smeared onto microscope slides, heat fixed and then hybridized for 30 minutes. Unhybridized PNA probe was removed by washing and smears were examined by fluorescence microscopy. Evaluation of the PNA FISH method using smears of 79 C. dubliniensis and 70 C. albicans strains showed 100% specificity for both PNA probes. It is concluded that PNA FISH is a powerful tool for the differentiation of C. albicans and C. dubliniensis.