Molecular epidemiology of Candida infections

During the last decade, nosocomial systemic yeast infections, especially those caused by Candida species, have been encountered increasingly often. For epidemiological purposes these infections can be categorised as type 1, from exogenous sources and type 2, of endogenous origin. Each type demands different infection-control approaches. Since systemic yeast infections are associated with high mortality, detailed knowledge of the epidemiology is of utmost importance. Yeast strain typing is one of the most important tools in such epidemiological investigations. Earlier studies used typing methods based on phenotypic characteristics. More recently typing methods analysing the genomic DNA of yeast strains have been introduced which, in general, appear to have a higher discriminatory power. Despite this, there are disadvantages such as lack of standardisation, and they are complex and time-consuming. Consequently, they cannot be applied in every laboratory. The optimal typing method remains to be defined and may vary depending on the species. Using all currently available techniques, however, knowledge of the epidemiology of yeast infections is increasing. For example, most infected patients harbour only one strain and the use of genotyping has provided evidence that the endogenous nora is a source of invasive pathogens. Clusters of Candida infections have also been reported in which exogenous sources or nosocomial acquisition have been determined by genotypic analysis. Finally, attempts have been made to correlate genotype with phenotype and virulence. In one such study some virulence phenotypes were shown to occur more frequently with certain genotypes. However, a correlation between genotype and virulence has not yet been firmly established. (C) 1999 Lippincott Williams & Wilkins.