title: Antimicrobial resistance and virulence genes of Escherichia coli isolates from swine in Ontario.
abstract: A total of 318 Escherichia coli isolates obtained from diarrheic and healthy pigs in Ontario from 2001 to 2003 were examined for their susceptibility to 19 antimicrobial agents. They were tested by PCR for the presence of resistance genes for tetracycline, streptomycin, sulfonamides, and apramycin and of 12 common virulence genes of porcine E. coli. Antimicrobial resistance frequency among E. coli isolates from swine in Ontario was moderate in comparison with other countries and was higher in isolates from pigs with diarrhea than in isolates from healthy finisher pigs. Resistance profiles suggest that cephamycinases may be produced by > or = 8% of enterotoxigenic E. coli (ETEC). Resistance to quinolones was detected only in enterotoxigenic E. coli (< or = 3%). The presence of sul3 was demonstrated for the first time in Canada in porcine E. coli isolates. Associations were observed among tetA, sul1, aadA, and aac(3)IV and among tetB, sul2, and strA/strB, with a strong negative association between tetA and tetB. The paa and sepA genes were detected in 92% of porcine ETEC, and strong statistical associations due to colocation on a large plasmid were observed between tetA, estA, paa, and sepA. Due at least in part to gene linkages, the distribution of resistance genes was very different between ETEC isolates and other porcine E. coli isolates. This demonstrates that antimicrobial resistance epidemiology differs significantly between pathogenic and commensal E. coli isolates. These results may have important implications with regards to the spread and persistence of resistance and virulence genes in bacterial populations and to the prudent use of antimicrobial agents.
authors.affiliation: Department of Pathobiology, University of Guelph, Ontario N1G 2W1, Canada. pboerlin@uoguelph.ca
authors.forename: Patrick
authors.initials: P
authors.lastname: Boerlin
authors.forename: Rebeccah
authors.initials: R
authors.lastname: Travis
authors.forename: Carlton L
authors.initials: CL
authors.lastname: Gyles
authors.forename: Richard
authors.initials: R
authors.lastname: Reid-Smith
authors.forename: Nicol
authors.initials: N
authors.lastname: Janecko
authors.forename: Heather
authors.initials: H
authors.lastname: Lim
authors.forename: Vivian
authors.initials: V
authors.lastname: Nicholson
authors.forename: Scott A
authors.initials: SA
authors.lastname: McEwen
authors.forename: Robert
authors.initials: R
authors.lastname: Friendship
authors.forename: Marie
authors.initials: M
authors.lastname: Archambault
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D003967:Diarrhea / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary*; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification / Q000472:pathogenicity*; D004927:Escherichia coli Infections / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary; D029968:Escherichia coli Proteins / Q000235:genetics*; D008826:Microbial Sensitivity Tests / Q000379:methods / Q000592:standards; D009864:Ontario / Q000453:epidemiology; D016133:Polymerase Chain Reaction / Q000379:methods; D013552:Swine; D013553:Swine Diseases / Q000453:epidemiology* / Q000382:microbiology; D014774:Virulence
chemical_list: D000900:Anti-Bacterial Agents; D029968:Escherichia coli Proteins