Genetic characterization of clinical and agri-food isolates of multi drug resistant Salmonella enterica serovar Heidelberg from Canada

doi:10.1186/1471-2180-8-89

BMC Microbiology
Volume 8

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Andrysiak AK
Olson AB
Tracz DM
Dore K
Irwin R
Ng LK
Gilmour MW

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Olson AB
Tracz DM
Dore K
Irwin R
Ng LK
Gilmour MW
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Research article

Genetic characterization of clinical and agri-food isolates of multi drug resistant Salmonella enterica serovar Heidelberg from Canada

Ashleigh K Andrysiak¹^,2 , Adam B Olson¹ , Dobryan M Tracz¹ , Kathryn Dore³ , Rebecca Irwin⁴ , Lai-King Ng¹^,2 , Matthew W Gilmour¹^,2 and Canadian Integrated Program for Antimicrobial Resistance Surveillance Collaborative

¹Bacteriology and Enteric Diseases Program, National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg, MB, Canada

²Department of Medical Microbiology, University of Manitoba, Winnipeg, MB, Canada

³Foodborne, Waterborne and Zoonotic Infections Division, Public Health Agency of Canada, Guelph, ON, Canada

⁴Laboratory for Foodborne Zoonoses (LFZ), Public Health Agency of Canada, St-Hyacinthe, QC and Guelph, ON, Canada

author email corresponding author email

BMC Microbiology 2008, 8:89doi:10.1186/1471-2180-8-89


Published:	6 June 2008

Abstract

Background

Salmonella enterica serovar Heidelberg ranks amongst the most prevalent causes of human salmonellosis in Canada and an increase in resistance to extended spectrum cephalosporins (ESC) has been observed by the Canadian Integrated Program for Antimicrobial Resistance Surveillance. This study examined the genetic relationship between S. Heidelberg isolates from livestock, abattoir, retail meat, and clinical human specimens to determine whether there was a link between the emergence of MDR S. Heidelberg in chicken agri-food sources and the simultaneous increase of MDR S. Heidelberg in human clinical samples.

Results

Chromosomal genetic homogeneity was observed by pulsed-field gel electrophoresis (PFGE), DNA sequence-based typing (SBT) and DNA microarray-based comparative genomic hybridization (CGH). Sixty one percent of isolates were indistinguishable by PFGE conducted using XbaI and BlnI restriction enzymes. An additional 15% of isolates had PFGE patterns that were closely related to the main cluster. SBT did not identify DNA polymorphisms and CGH revealed only genetic differences between the reference S. Typhimurium strain and S. Heidelberg isolates. Genetic variation observed by CGH between S. Heidelberg isolates could be attributed to experimental variation. Alternatively, plasmid content was responsible for differences in antimicrobial susceptibility, and restriction fragment length polymorphism (RFLP) analyses followed by replicon typing identified two divergent plasmid types responsible for ESC resistance.

Conclusion

Due to the overall limited genetic diversity among the isolates, it was not possible to identify variable traits that would be suitable for source tracking between human and agri-food isolates of S. Heidelberg in Canada.