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Title: The population structure of the Corynebacterium diphtheriae group
Author: Bolt, Frances
ISNI:       0000 0004 2680 0911
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 2009
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A multi-locus sequence typing scheme was designed for the Corynebacterium diphtheriae group comprising C. diphtheriae, C. ulcerans and C. pseudotuberculosis. Five MLST genes (atpA, dnaE, fusA, odhA and rpoB) were analysed to resolve the inter-species relationships of the three organisms. No alleles were shared between the species and MLSA analysis indicated that they represent distinct populations with no evidence of recombination between the organisms. One hundred and fifty four C. diphtheriae isolates were analysed by MLST using the same five loci and two additional genes (dnaK and leuA). The data derived was in concordance with previous ribotyping studies and identified two clonal complexes associated with diphtheria outbreaks. No correlation between ST and toxin production or clinical presentation was observed. In contrast to the biovars gravis, mitis and intermedius the atypical belfanti strains were distinct by phylogenetic analysis. Although two C. diphtheriae cultures isolated from a horse clustered with the human strains four isolates obtained from two cats shared no alleles with the other isolates examined. MLST analysis of 69 C. ulcerans isolates using the five MLST genes and the virulence determinant phospholipase D (PLD) revealed that veterinary and human isolates were not genetically distinct. As with the C. diphtheriae population recombination was shown to play an important role in the evolution of the organism. The 73 C. pseudotuberculosis isolates were examined with the five MLST loci, pld and two genes within the Fe acquisition operon; fagCand fagD. The nitrate negative and positive strains were distinguished by MLST but shared ancestry was apparent as the same alleles were identified in two to three of the genes. MLST supported previous studies which indicate that C. pseudotuberculosis biovar ovis is a genetically homogenous species. This is the first MLST scheme designed for the C. diphtheriae group and the first to encompass multiple species within the Corynebacterium genus. MLST provides a useful tool for the discrimination of the three species and will enable the detection of genetic exchange events between and within the organisms.
Supervisor: Not available Sponsor: Biotechnology and Biological Sciences Research Council (Great Britain) (BBSRC)
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QH426 Genetics