Rapid Identification of Candida dubliniensis Using a Species-Specific Molecular Beacon

Candida dubliniensis is an opportunistic fungal pathogen that has been linked to oral candidiasis in AIDS patients, although it has recently been isolated from other body sites. DNA sequence analysis of the internal transcribed spacer 2 (ITS2) region of rRNA genes from referenceCandida strains was used to develop molecular beacon probes for rapid, high-fidelity identification ofC. dubliniensis as well asC. albicans . Molecular beacons are small nucleic acid hairpin probes that brightly fluoresce when they are bound to their targets and have a significant advantage over conventional nucleic acid probes because they exhibit a higher degree of specificity with better signal-to-noise ratios. When applied to an unknown collection of 23 strains that largely containedC. albicans and a smaller amount ofC. dubliniensis , the species-specific probes were 100% accurate in identifying both species following PCR amplification of the ITS2 region. The results obtained with the molecular beacons were independently verified by random amplified polymorphic DNA analysis-based genotyping and by restriction enzyme analysis with enzymesBsm AI andNsp BII, which cleave recognition sequences within the ITS2 regions ofC. dubliniensis andC. albicans , respectively. Molecular beacons are promising new probes for the rapid detection ofCandida species.