Assessment of Candida glabrata strain relatedness by pulsed-field gel electrophoresis and multilocus sequence typing

Abstract

In this study, 80 Candida glabrata isolates from intensive care unit and human immunodeficiency virus (HIV)-infected patients were typed by multilocus sequence typing (MLST), pulsed-field gel electrophoresis (PFGE), and mating type class determination. Among the 25 patients with multiple isolates, 19 patients (76%) contained multiple isolates exhibiting identical or highly related PFGE and MLST genotypes, which may indicate the maintenance or microvariation of one C. glabrata strain in each patient. However, isolates from six patients (24%) displayed different sequence types, PFGE genotypes, or mating type classes, which may indicate colonization with more than one clone over time or strain replacement. High correlations among PFGE genotypes, sequence types, and mating types were found (P < 0.01). MLST exhibited less discriminatory power than PFGE with BssHII. The genotypes, sequence types, and mating type classes were independent of anatomic sources, drug susceptibility, and HIV infection status.

FIG. 1.

Dendrogram indicating the similarities of the 80 C. glabrata isolates determined by MLST with six gene fragments. Groups were defined by a sequence similarity of 99.7% and bootstrap values of >90%.

FIG. 2.

Dendrogram indicating the similarities of the 80 C. glabrata isolates determined by PFGE of fragments restricted with BssHII. Groups were defined by DNA pattern similarity of 90%.