Comparative genomics to identify genetic variabilities associated with Salmonella Typhimurium DT104 epidemicity

Mark Saunders

Research output: ThesisDoctoral Thesis

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Non-typhoidal Salmonella epidemics have a huge impact on animal and human health. During the 1980’s a new epidemic strain emerged, S. Typhimurium DT104, first in the UK but later spreading through Europe and North America. This phage type displayed resistance to a panel of antibiotics and was isolated from cattle, pigs and poultry as well as from human clinical infections. By the 2000’s, infections by this strain were subsiding, while other epidemic strains of Salmonella were emerging.
This study used Comparative Genomic Hybridisation (CGH) arrays to screen DT104 strains from before, during and after the epidemic period, to interrogate the genetic changes that may have contributed to the strain epidemicity. Two novel techniques, optical mapping and the Biolog phenotypic microarray, were used to confirm or refute the CGH results. The study found that the major difference between pre-epidemic and epidemic strains was the acquisition of the antibiotic resistance carrying Salmonella Genomic Island 1 (SGI1). This region showed increased variation towards the latter period. In addition, genes involved in the theorised production of a ‘pertussis like’ toxin were found to be present in human epidemic strains, while they varied or were missing from strains of animal origin and human pre-epidemic sensitive strains. Other differences were found in the presence of genes for allantoin and glyoxylate utilisation for strains that may represent an ancestral clone of DT104. The CGH results revealed variation and this variation was confirmed by phenotypic assay and confirmatory techniques.
Overall the picture of DT104 epidemicity is complex, but this study has identified areas of potential importance and has suggested avenues of research, that may lead to a deeper understanding of how epidemics develop.
Original languageEnglish
Awarding Institution
  • Royal Holloway, University of London
  • Bramley, Peter, Supervisor
Award date1 Apr 2013
Publication statusUnpublished - 16 Apr 2013

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