Infection with a Candida albicans general-purpose genotype is associated with higher mortality in young patients

The yeast Candida albicans causes life-threatening infections in immunocompromised patients. Epidemiological and phylogenetic studies have revealed the existence of a general-purpose genotype (GPG, corresponding to clade 1), which causes infections more frequently than other genotypes. The high prevalence might indicate that GPG strains are also more virulent and thus associated with higher mortality. To investigate this we developed a duplex PCR assay based on GPG-specific mutations, which was 97% accurate in identifying GPG strains in an international collection of strains typed with the probe Ca3. We applied this assay to 660 candidemia isolates, predominantly from Italy and France. Three percent of isolates were untypeable, and 4% produced an intermediate genotype. Of the remaining 610 isolates 19% could be clearly attributed to the GPG group, the remainder showed the PCR pattern characteristic of non-GPG strains. These numbers are in agreement with the genotype distribution in earlier studies, indicating that the method reliable identified GPG strains in the current sample. Across the entire patient cohort there was no difference in the mortality of patients infected with GPG strain and other strains (40% in both cases). However mortality in patients up to the age of 40 was 43% when infected with GPG strains, but only 19% when infected with other strains (z test, P<0.01). Mortality associated with GPG and non-GPG strains was comparable in older patients. Prevalence of GPG strains was also increased in younger patients, in particular in infants (35%). A logistic regression analysis confirmed the age-dependent impact of genotype on mortality.