Comparative genotyping of Candida albicans bloodstream and nonbloodstream isolates at a polymorphic microsatellite locus

Molecular typing studies have shown that the predominant form of reproducti on of Candida albicans is clonal and that, in a majority of situations, per sistent or recurrent infections are due to a unique strain. Characterizatio n of distinct subpopulations and correlation with clinical features may thu s be important to understanding the pathogenesis of candidiasis. In a clona l model, a unique polymorphic marker may identify populations with differen t biological properties. We therefore compared 48 bloodstream isolates and 48 nonbloodstream matched strains of C. albicans at the elongation factor 3 -encoding gene (CEF3) polymorphic microsatellite locus of C. albicans. Sizi ng of the alleles was performed by automated capillary electrophoresis. A n ew, 137 bp allele was characterized, and seven nondescribed combinations we re observed, resulting in 15 and 11 distinct CEM profiles in bloodstream an d control strains, respectively. Genotypes 126-135, 130-136, and 131-131 ac counted for 60.4% of both bloodstream and control strains. Four bloodstream isolates but no control strains displayed the 135-135 combination. None of the other genotypes was present at an increased frequency in bloodstream i solates. Bloodstream and nonbloodstream strains of C. albicans thus have a heterogeneous structure at the CEF3 locus, with three major and multiple mi nor allelic combinations.