title: Associations between antimicrobial resistance genes in fecal generic Escherichia coli isolates from cow-calf herds in western Canada.
abstract: The objective of this study was to examine associations among the genetic determinants of antimicrobial resistance (AMR) in 207 fecal generic Escherichia coli isolates obtained from 77 cow-calf herds in western Canada. Twenty-three resistance genes corresponding to six different antimicrobial families were assessed using DNA hybridization and PCR. The most common resistance genes in the study sample (207 isolates) were sul2 (48.3%), tet(B) (45.4%), and ant(3'')-Ia (aadA1) (19.3%). Several statistically significant associations between the examined resistance genes were detected. The strongest associations observed were those between genes for resistance to chloramphenicol (catI) and trimethoprim (dhfrI) (odds ratio [OR] = 214; P = 0.0001), sulfonamide (sul1) and chloramphenicol (catI) (OR = 96.9; P = 0.0001), streptomycin [ant(3'')-Ia (aadA1)] and trimethoprim (dhfrI) (OR = 96.2; P = 0.0001), sulfonamide (sul1) and streptomycin [ant(3'')-Ia (aadA1)] (OR = 79.3; P = 0.0001), and tetracycline [tet(B)] and sulfonamides (sul2) (OR = 25.7; P = 0.0001). At least one of the resistance genes corresponding to each nonaminoglycoside family of antimicrobials examined in this study was associated with the two aminoglycoside resistance genes ant(3'')-Ia (aadA1) and aph(3')-Ia. The multiple, strong associations between genes and the diverse nature of the associations described in this study demonstrate the complexity of resistance gene selection in cow-calf herds and should be considered in the planning of AMR control practices for cow-calf operations.
authors.affiliation: Department of Large Animal Clinical Sciences, Western College of Veterinary Medicine, 52 Campus Dr., Saskatoon, Saskatchewan S7N 5B4, Canada. sheryl.gow@usask.ca
authors.forename: Sheryl P
authors.initials: SP
authors.lastname: Gow
authors.forename: Cheryl L
authors.initials: CL
authors.lastname: Waldner
authors.forename: Josee
authors.initials: J
authors.lastname: Harel
authors.forename: Patrick
authors.initials: P
authors.lastname: Boerlin
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002170:Canada; D002417:Cattle; D004269:DNA, Bacterial / Q000235:genetics; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D004926:Escherichia coli / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification*; D005243:Feces / Q000382:microbiology*; D005798:Genes, Bacterial; D005838:Genotype; D008826:Microbial Sensitivity Tests; D009693:Nucleic Acid Hybridization / Q000379:methods; D016133:Polymerase Chain Reaction / Q000379:methods
chemical_list: D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial