A DNA polymorphism specific to Candida albicans strains exceptionally successful as human pathogens

A large proportion of infection-causing isolates of the yeast Candida albic ans belong to a general-purpose genotype, identifiable by fingerprinting wi th the moderately repetitive sequence CO. The high prevalence of this group - up to 70% in some patient categories suggests that its members possess g enetic determinants. which enhance their success as pathogens compared to o ther strains. To find such determinants we are comparing the genomes of rep resentatives of the general-purpose genotype cluster with the genomes of ot her strains. In this paper we describe the identification of a 985 bp HpaII fragment (MU13-4) specific to general-purpose genotype strains. The fragme nt was present in 90% of these strains, but only in 10% of other strains. T he fragment did not hybridize with probe Ca3, used to define the general-pu rpose cluster. It contains elevated levels of repetitive DNA. Sequences hom ologous to MU 13-4 are dispersed throughout the chromosomes of general-purp ose strains but are rarer or absent in other strains, as judged by Southern hybridization. Using the Stanford C. albicans genome database, we have pla ced the MU 13-4 fragment next to a CARE-1 element. We also found 79 signifi cant homologies between parts of MU13-4 and 19 other contigs. Attempts to a mplify the region surrounding the polymorphic fragment in non-general-purpo se genotype strains suggest. as do the hybridization data, that the polymor phism is created by a deletion in non-cluster strains. These results show t hat it is possible to identify polymorphisms specific to general-purpose ge notype strains. Primers against the fragment will allow PCR-based discrimin ation between general-purpose genotype strains and other strains, facilitat ing investigations aimed at determining morbidity and mortality caused by g eneral-purpose genotype strains compared to other strains. (C) 2001 Elsevie r Science B.V. All rights reserved.