Evidence for a general-purpose genotype in Candida albicans, highly prevalent in multiple geographical regions, patient types and types of infection

Epidemiological studies, using the probe Ca3, have shown that in a given pa tient population a single cluster of genetically related Candida albicans i solates usually predominates. The authors have investigated whether these l ocal clusters are part of a single group, geographically widespread and hig hly prevalent as an aetiological agent of various types of candidiasis. An unrooted neighbour-joining tree of 266 infection-causing C. albicans isolat es (each from a different individual) from 12 geographical regions in 6 cou ntries was created, based on genetic distances generated by Ca3 fingerprint ing. Thirty-seven per cent of all isolates formed a single genetically homo geneous cluster (cluster A). The remainder of isolates were genetically div erse. Using the maximum branch length within cluster A as a cut-off, they c ould be divided into 37 groups, whose prevalence ranged between 0.3 % and 9 %. Strains from cluster A were highly prevalent in all but one geographica l region, with a mean prevalence across all regions of 41 %. When isolates were separated into groups based on patient characteristics or type of infe ction, strains from cluster A had a prevalence exceeding 27 % in each group , and their mean prevalence was 43 % across all patient characteristics. Th ese data provide evidence that cluster A constitutes a general-purpose geno type, which is geographically widespread and acts as a predominant aetiolog ical agent of all forms of candidiasis in all categories of patients survey ed.