Submitted to: Interscience Conference on Antimicrobial Agents & Chemotherapy Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 9/25/2001
Publication Date: N/A
Technical Abstract: The recent discovery of Candida dubliniensis as a separate species that traditionally has been identified as Candida albicans has lead 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 offers significant advantages in whole cell in situ hybridization assays. In this study, we designed two PNA probes targeting the rRNA of C. albicans and C. dubliniensis, respectively, 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 in parallel with each of the two PNA probes both labeled with fluorescein. Unhybridized PNA probe was removed by washing and smears were examined by fluorescence microscopy. The method was evaluated with 103 well-characterized clinical isolates and correctly identified 42 isolates as C. albicans and 59 isolates as C. dubliniensis whereas results obtained with the remaining 2 isolates were inconclusive. None of the isolates were incorrectly identified. It is concluded that PNA FISH is a powerful tool for the differentiation of C. albicans and C. dubliniensis.