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P2-17 Differential Distribution of SNP Lineages in Australian and U.S. Eschericha coli O157 Isolates

Tuesday, August 5, 2014
Exhibit Hall D (Indiana Convention Center)
Glen Mellor, CSIRO, Brisbane, Australia
Smriti Shringi, Washington State University, Pullman, WA
Margaret Davis, Washington State University, Pullman, WA
Brittany Beavis, Washington State University, Pullman, WA
WooKyung Jung, Washington State University, Pullman, WA
Helen Smith, QHFSS, Brisbane, Australia
Amy Jennison, QHFSS, Brisbane, Australia
Christine Doyle, QHFSS, Brisbane, Australia
Kari Gobius, CSIRO, Werribee, Australia
Robert Barlow, CSIRO, Brisbane, Australia
Narelle Fegan, CSIRO, Werribee, Australia
Thomas Besser, Washington State University, Pullman, WA
Introduction: Escherichia coli O157 is a foodborne pathogen that has been isolated from many different countries. Recent analyses have used single nucleotide polymorphisms (SNPs) to classify E. coli O157 isolates into specific lineages that are associated with animals (termed bovine-biased lineages) and humans (termed clinical lineages), but little is known about genetic variation between different countries. 

Purpose: Here, we investigate the distribution of cattle and human associated SNP lineages in E. coli O157 isolates from Australia and the U.S.A. 

Methods: Ninety-eight E. coli O157 isolates (comprising 24 cattle and 25 clinical sources from each country) were screened for the presence of SNPs using a 48-plex Golden Gate assay system which was subsequently used to assign isolates to 11 SNP lineages. 

Results: E. coli O157 isolates from both countries largely segregated into different SNP lineages. The predominant SNP lineages observed in the U.S.A. were also present in Australia, albeit at much lower frequencies. In contrast, the predominant SNP lineages in Australia (IVb; 48% and IVcvar; 30%) were not detected in this U.S.A. isolate set. The IVcvar SNP lineage represents a unique variant that appears to be exclusive to Australia. Overall, a significantly (P < 0.05) higher proportion of U.S.A. isolates (72%) belonged to clinically defined SNP lineages than Australian isolates (4%).

Significance: This study supports previous suggestions that very few Australian E. coli O157 isolates belong to the clinical types observed in the United States. The discovery of a new SNP lineage (IVcvar) in Australian isolates suggests that the genotypic diversity of E. coli O157 may differ worldwide. Therefore, development of future genotyping methods would benefit from using a globally sourced E. coli O157 strain set to ensure that maximum genotypic diversity is captured.

Back to: Poster Session - Pathogens, Epidemiology, Novel Laboratory Methods, Food Defense, Communication Outreach and Education, General Microbiology, Dairy and Other Food Commodities, Food Toxicology
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