Multilocus sequence type analysis reveals both clonality and recombination in populations of Candida glabrata bloodstream isolates from U.S. surveillance studies

Abstract

The human commensal yeast Candida glabrata is becoming increasingly important as an agent of nosocomial bloodstream infection. However, relatively little is known concerning the genetics and population structure of this species. We have analyzed 230 incident bloodstream isolates from previous and current population-based surveillance studies by using multilocus sequence typing (MLST). Our results show that in the U.S. cities of Atlanta, GA; Baltimore, MD; and San Francisco, CA during three time periods spanning 1992 to 2009, five populations of C. glabrata bloodstream isolates are defined by a relatively small number of sequence types. There is little genetic differentiation in the different C. glabrata populations. We also show that there has been a significant temporal shift in the prevalence of one major subtype in Atlanta. Our results support the concept that both recombination and clonality play a role in the population structure of this species.

Fig. 1.

Neighbor-joining trees for each population in this study showing the abundance of each genotype in the population. (A) Atlanta, 1992; (B) Atlanta, 2008; (C) Baltimore, 1998; (D) Baltimore, 2008; (E) San Francisco, 1992. Circles represent the percentage of each population of a given ST. Major STs ST3, ST16, and ST19 are shaded in gray or black.

Fig. 2.

Neighbor-joining dendrogram for the 31 STs identified in this study. Major groups previously identified (4) are indicated. Horizontal bar indicates percent divergence. Bootstrap values above 60% are indicated at nodes (replicates = 1,000).