Strain-relatedness among different populations of the pathogenic yeast Candida albicans analyzed by DNA-based typing methods.

A pathogenic yeast Candida albicans is one of the most frequently isolated microorganisms in patients suffering from opportunistic infection. The typing of the isolates is important not only to elucidate the route of infection but to explore the evolution of the pathogenic yeast. This article presents an overview of recent research on the strain typing in different populations of C. albicans using the following DNA-based methods: electrophoretic karyotyping by pulsed field gel electrophoresis (PFGE), restriction fragment length polymorphism (RFLP) of digests of genomic DNA by restriction enzymes (with or without Southern hybridization with a DNA probe) and amplification of random or specific sequences by using polymerase chain reaction (PCR). The results of these methods were compared for strain discrimination. Studies on the genetic diversity of the strains among different individuals in a single population cohort, and among different populations of healthy carriers and immunocompetent and immunocompromised patients, were reviewed. Typing of the strains recurrently isolated through the episodes of diseases such as vaginitis and AIDS revealed the occurrence of strain variation or microevolution. Typing of isolates from nosocomial infections indicated the possible occurrence of horizontal transmission of the disease within a single hospital. In addition, recent studies suggested a possible mechanism that might involve the C. albicans-specific repetitive sequences, RPSs, for chromosome rearrangements leading to strain variation.