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J Food Prot. 2014 Jan;77(1):40-9. doi: 10.4315/0362-028.JFP-13-251.

Antibiotic resistance and diversity of Salmonella enterica serovars associated with broiler chickens.

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Pacific Agri-Food Research Centre, Agriculture and Agri-Food Canada, Agassiz, British Columbia, Canada V0M 1A0.
Pacific Agri-Food Research Centre, Agriculture and Agri-Food Canada, Summerland, British Columbia, Canada V0H 1Z0.
Lacombe Research Centre, Agriculture and Agri-Food Canada, 6000 C & E Trail, Lacombe, Alberta, Canada T4L 1W1.
British Columbia Ministry of Agriculture, Abbotsford, British Columbia, Canada V3G 2M3.
Southern Crop Protection and Food Research Centre, Agriculture and Agri-Food Canada, London, Ontario, Canada N5V 4T34.


The objective of this study was to analyze the antibiotic resistance phenotype and genotype of Salmonella isolated from broiler production facilities. A total of 193 Salmonella isolates recovered from commercial farms in British Columbia, Canada, were evaluated. Susceptibility to antibiotics was determined with the Sensititre system. Virulence and antibiotic resistance genes were detected by PCR assay. Genetic diversity was determined by pulse-field gel electrophoresis (PFGE) typing. Seventeen serovars of Salmonella were identified. The most prevalent Salmonella serovars were Kentucky (29.0% of isolates), Typhimurium (23.8%), Enteritidis (13.5%), and Hadar (11.9%); serovars Heidelberg, Brandenburg, and Thompson were identified in 7.7, 4.1, and 3.6% of isolates, respectively. More than 43% of the isolates were simultaneously resistant to ampicillin, amoxicillin-clavulanic acid, ceftiofur, cefoxitim, and ceftriaxone. This β-lactam resistance pattern was observed in 33 (58.9%) of the Salmonella Kentucky isolates; 2 of these isolates were also resistant to chloramphenicol, streptomycin, sulfisoxazole, and tetracycline. Genes associated with resistance to aminoglycosides (aadA1, aadA2, and strA), β-lactams (blaCMY-2, blaSHV, and blaTEM), tetracycline (tetA and tetB), and sulfonamide (sul1) were detected among corresponding resistant isolates. The invasin gene (invA) and the Salmonella plasmid virulence gene (spvC) were found in 97.9 and 25.9% of the isolates, respectively, with 33 (71.7%) of the 46 Salmonella Typhimurium isolates and 17 (65.4%) of the 26 Salmonella Enteritidis isolates carrying both invA and spvC. PGFE typing revealed that the antibiotic-resistant serovars were genetically diverse. These data confirm that broiler chickens can be colonized by genetically diverse antibiotic-resistant Salmonella isolates harboring virulence determinants. The presence of such strains is highly relevant to food safety and public health.

[Indexed for MEDLINE]

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