MLST OF CANDIDA GLABRATA REVEALS GEOGRAPHICALLY SPECIFIC CLADES

Dodgson AR 1 ,Pujol C 2 , Anderson MA 1 , Fox AJ 3 , Soll DR 2 , Denning DW 1

Author address: 

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Abstract: 

Candida glabrata is the second most common Candida species causing bloodstream infection, after C. albicans. Systemic C. glabrata infections are characterised by a high crude mortality rate and reduced susceptibility to fluconazole. Despite this, little is known of the epidemiology or population structure of this species. Population biologists regard sequence based typing techniques to be amongst the fingerprinting methods best suited for the study of population genetics. We developed a MultiLocus Sequence Typing (MLST) scheme for C. glabrata, and used it to fingerprint a geographically diverse collection of isolates. To identify appropriate loci, fragments of the coding regions of 11 C. glabrata genes were amplified and sequenced in 10 unrelated isolates. The 6 most variable loci (FKS, LEU2, NMT1, TRP1, UGP1 and URA3) were then sequenced in a collection of 110 isolates (64 European, 28 American, 14 Japanese and 2 Chilean, and 2 reference strains). From the 3345bp sequenced in each isolate, 81 nucleotide sites were found to be variable. These defined 30 Sequence Types (ST’s) among the 110 strains. The relationships between the ST’s identified were visualized by generating a dendrogram of the whole collection from the matrix of pairwise similarity obtained for the 3345bp concatenated DNA sequence (a composite of the sequences from all 6 loci) using the Unweighted Pair Group Method with Arithmetic averages (UPGMA). Assessment of the significance of the nodes was done by bootstrapping with 1000 randomisations, only the polymorphic sites were used for the bootstrap analysis. In this dendrogram, 12 nodes presented higher than 60% confidence in bootstrap analysis. These nodes were all found below a DNA sequence similarity threshold of 99.6%. We used this threshold to distinguish 5 major groups (I to V) in the collection of isolates analyzed. Significant (P
2003

abstract No: 

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Full conference title: 

The 15 th Congress of the International Society for Human and Animal Mycology
    • ISHAM 15th (2003)