We submitted a panel of 416 isolates of Candida albicans from separate sources to multilocus sequence typing
(MLST). The data generated determined a population structure in which four major clades of closely related
isolates were delineated, together with eight minor clades comprising five or more isolates. By Fisher’s exact
test, a statistically significant association was found between particular clades and the anatomical source,
geographical source, ABC genotype, decade of isolation, and homozygosity versus heterozygosity at the mating
type-like locus (MTL) of the isolates in the clade. However, these associations may have been influenced by
confounding variables, since in a univariate analysis of variance, only the clade associations with ABC type and
anatomical source emerged as statistically significant, providing the first indication of possible differences
between C. albicans strain type clades and their propensity to infect or colonize different anatomical locations.
There were no significant differences between clades with respect to distributions of isolates resistant to
fluconazole, itraconazole, or flucytosine. However, the majority of flucytosine-resistant isolates belonged to
clade 1, and these isolates, but not flucytosine-resistant isolates in other clades, bore a unique mutation in the
FUR1 gene that probably accounts for their resistance. A significantly higher proportion of isolates resistant
to fluconazole, itraconazole, and flucytosine were homozygous at the MTL, suggesting that antifungal pressure
may trigger a common mechanism that leads both to resistance and to MTL homozygosity. The utility of MLST
for determining clade assignments of clinical isolates will form the basis for strain selection for future research
into C. albicans virulence