[Molecular biological differentiation of yeasts]

Regarding the rise and the epidemiological shifts in Candida infections, accurate and rapid identification of yeasts to species level is exceedingly important. Furthermore, non-albicans species (e.g. C. glabrata, C. dubliniensis, C. inconspicua, C. krusei and C. norvegensis) have recently emerged as azole-resistant pathogens. Standard methods for cultivation and differentiation of Candida species are time-consuming, often insensitive and can fail to distinguish non-albicans species. To overcome low sensitivity, poor specificity and untolerable delay, molecular tools to the diagnosis of Candida infection have been adopted, particularly the polymerase chain reaction (PCR). Several genus and species specific amplification-based diagnostic methods for detection of medically important yeasts have been published. As the incidence of nosocomial Candida infections has been risen significantly, typing has become increasingly important in candidal epidemiology to define infectious processes as well as sources and modes of transmission. For the development of rational infection-control measures, modern genotyping methods based on genomic DNA polymorphism (e.g. pulsed-field gel electrophoresis, DNA amplification-based methods) have replaced conventional physiological techniques. However, reliability, sensitivity and efficiency of genotyping methods have been controversially discussed and these DNA-based methods are mostly insufficiently standardized. Criteria as typeability, reproducibility and discriminatory power should be considered in evaluating typing systems.