Molecular genetic approaches to identification, epidemiology and taxonomy of non-albicans Candida species

Abstract

The reported incidence of fungal infections associated with non-albicans species from the Candida genus is increasing. Most of these infections occur in immunocompromised patients, particularly those infected with HIV. The role of molecular genetic techniques alongside the existing techniques for the identification and typing of these organisms is discussed. Species-specific genomic DNA fragments cloned from C. tropicalis and C. krusei have been developed for identification and strain typing. Analysis of tRNA profiles has been shown to be effective for the identification of C. glabrata, C. guilliermondii, C. parapsilosis and C. tropicalis. A PCR method employing primers complimentary to large ribosomal subunit genes and the lanosterol-alpha-demethylase gene has been applied for several species, including C. glabrata, C. krusei and C. tropicalis. Strain typing by comparison of genomic DNA fingerprints has been demonstrated for C. tropicalis and C. krusei following hybridisation analysis with species-specific probes. Synthetic oligonucleotide probes--which do not have to be species-specific and which can detect minor polymorphisms--have also been used for strain typing of isolates of several non-albicans species. Random amplification of polymorphic DNA (RAPD) has also been used for analysis of C. glabrata, C. lusitaniae and C. tropicalis isolates. The potential for the application of these and other techniques to Candida spp. taxonomy--and the example of a recently discovered novel species, C. dubliniensis--is discussed.