Molecular epidemiology and antimicrobial resistance of Salmonella Typhimurium DT104 on Ontario swine farms

Abdolvahab Farzan, Robert M. Friendship, Cornelis Poppe, Laura Martin, Catherine E. Dewey, Julie Funk

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


This study was conducted to examine antimicrobial resistances, plasmid profiles, and pulsed-field gel electrophoresis patterns of 80 Salmonella Typhimurium (including var. Copenhagen) DT104 strains (including DT104a and DT104b) recovered from pig and environmental fecal samples on 17 swine farms in Ontario. No resistance was observed to amoxicillin/ clavulanic acid, apramycin, carbadox, cephalothin, ceftriaxone, ceftiofur, cefoxitin, ciprofloxacin, nalidixic acid, trimethoprim, and tobramycin. However, the isolates exhibited resistance against 4 to 10 antimicrobials with the most frequent resistance being to sulfonamides (Su), ampicillin (A), streptomycin (S), spectinomycin (Sp), chloramphenicol (C), tetracycline (T), and florfenicol (F). Thirteen distinct resistance patterns were determined but 88% of isolates shared the typical resistance pattern "ACSpSSuT." Twelve different plasmid profiles were observed; the 62 MDa virulence-associated plasmid was detected in 95% of the isolates. The 2.1 MDa plasmid was the second most frequent one, which was harbored by 65% isolates. The isolates were classified into 23 distinct genotypes by PFGE-SpeI + BlnI when difference in at least one fragment was defined as a distinct genotype. In total, 39 distinct "types" were observed when defining a "type" based on the combination of antimicrobial resistance, plasmid pattern, and PFGE-SpeI + BlnI for each isolate. The highest diversity was 0.96 (95% Cl: 0.92, 0.96) for the "type" described above followed by 0.92 (95% CI: 0.88, 0.93) for PFGE-Spel + BlnI. The diversity of DT104 isolates indicates there might be multiple sources for this microorganism on swine farms. This knowledge might be used to track these sources, as well as to study the extent of human salmonellosis attributed to pork compared to food products derived from other food-producing animals.

Original languageEnglish (US)
Pages (from-to)188-194
Number of pages7
JournalCanadian Journal of Veterinary Research
Issue number2 SPEC. ISS.
StatePublished - 2008
Externally publishedYes

ASJC Scopus subject areas

  • veterinary(all)


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