Endemic genotypes of Candida albicans causing fungemia are frequent in the hospital

Abstract

Genotyping of Candida albicans strains causing candidemia can uncover the presence of endemic genotypes in the hospital. Using a highly reproducible and discriminatory microsatellite marker panel, we studied the genetic diversity of 217 C. albicans isolates from the blood cultures of 202 patients with candidemia (from January 2007 to December 2011). Each isolate represented 1 candidemia episode. Multiple episodes were defined as the isolation of C. albicans in further blood cultures taken ≥7 days after the last isolation in blood culture. Of the 202 patients, 188 had 1 episode, 13 had 2 episodes, and 1 had 3 episodes. Identical genotypes showed the same alleles for all 6 markers. The genotypes causing both episodes were identical in most patients with 2 episodes (11/13; 84.6%). In contrast, 2 different genotypes were found in the patient with 3 episodes, one causing the first and second episodes and the other causing the third episode (isolated 6 months later). We found marked genetic diversity in 174 different genotypes: 155 were unique, and 19 were endemic and formed 19 clusters (2 to 6 patients per cluster). Up to 25% of the patients were infected by endemic genotypes that infected 2 or more different patients. Some of these endemic genotypes were found in the same unit of the hospital, mainly neonatology, whereas others infected patients in different wards.

Fig 1

Distribution of episodes of candidemia diagnosed in each year of the study period. The distribution of patients is also shown grouped by unit of admission at the time of diagnosis.

Fig 2

Minimum spanning tree showing the distribution of the 174 genotypes (circles) found in the strains studied and the number of strains belonging to the same genotype (larger circles indicate higher numbers). The connecting lines between the circles show the similarity between the profiles: the black lines indicate differences in only 1 marker, and the gray lines indicate differences in 2 or more markers. The numbers represent the cluster codes.

Fig 3

Timeline showing length of stay (months) for the patients involved in the 5 clusters in the neonatology unit. The numbers indicate the date of blood sample collection for each patient involved in the cluster.