title: Characterizing the Multidrug Resistance of non-O157 Shiga Toxin-Producing Escherichia coli Isolates from Cattle Farms and Abattoirs.
abstract: Non-O157 Shiga toxin-producing Escherichia coli (STECs) are not as well characterized as O157 STEC cases, despite their similar prevalence in many countries. Hence, the objective of this study was to investigate the phenotypic and genotypic basis of multidrug resistance (MDR) in non-O157 STEC farm- and abattoir-sourced isolates and assess the potential dissemination of these MDR profiles in vitro. Susceptibility testing to 20 antimicrobials was performed on 146 non-O157 STECs isolated from farm and abattoir environments. Eighty-seven percent of non-O157 STEC isolates were multidrug resistant to antimicrobials used during veterinary and agricultural practice. Antimicrobial resistance was significantly higher in abattoir isolates compared with the farm isolates (p < 0.05). Corresponding resistance determinants and integrons were investigated by polymerase chain reaction, with the predominant resistance determinants detected being floR, ampC, tet(A), blaTEM, and sul1. This is the first report of tet(G) in a non-O157 STEC isolate. Class 1 integrons were detected in 17 isolates. Resistance to ampicillin, cephalothin, chloramphenicol, kanamycin, neomycin, sulfonamides, trimethoprim, and tetracycline was associated with transferable plasmids belonging to incompatibility groups IncP, IncB/O, and IncFIB. Most MDR non-O157 STECs (90%) isolated in this study belong to phylogenetic groups A and B1. These findings suggest that MDR non-O157 STECs are emerging as a result of nonpathogenic E. coli acquiring virulence and resistance genes. This may convey a certain competitive advantage in the colonization of cattle when antimicrobial selective pressures are present, thereby leading to an increase in contamination of food with MDR non-O157 STECs.
authors.affiliation: 1 Cell Molecular Biology Laboratory, School of Veterinary Medicine, Veterinary Science Centre, University College Dublin , Dublin, Ireland .
authors.forename: Carrie-Ann
authors.initials: CA
authors.lastname: Kennedy
authors.affiliation: 2 UCD-Centre for Food Safety, School of Public Health, Physiotherapy and Sports Science, University College Dublin , Dublin, Ireland .
authors.forename: Séamus
authors.initials: S
authors.lastname: Fanning
authors.affiliation: 2 UCD-Centre for Food Safety, School of Public Health, Physiotherapy and Sports Science, University College Dublin , Dublin, Ireland .
authors.forename: Maria
authors.initials: M
authors.lastname: Karczmarczyk
authors.affiliation: 3 Teagasc, Ashtown Food Research Centre , Dublin, Ireland .
authors.forename: Brian
authors.initials: B
authors.lastname: Byrne
authors.affiliation: 3 Teagasc, Ashtown Food Research Centre , Dublin, Ireland .
authors.forename: Áine
authors.initials: Á
authors.lastname: Monaghan
authors.affiliation: 3 Teagasc, Ashtown Food Research Centre , Dublin, Ireland .
authors.forename: Declan
authors.initials: D
authors.lastname: Bolton
authors.affiliation: 1 Cell Molecular Biology Laboratory, School of Veterinary Medicine, Veterinary Science Centre, University College Dublin , Dublin, Ireland .
authors.forename: Torres
authors.initials: T
authors.lastname: Sweeney
mesh_terms: D000003:Abattoirs; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002417:Cattle; D024901:Drug Resistance, Multiple, Bacterial / Q000187:drug effects / Q000235:genetics*; D029968:Escherichia coli Proteins / Q000235:genetics*; D032023:Integrons / Q000235:genetics; D008826:Microbial Sensitivity Tests / Q000379:methods; D010802:Phylogeny; D010957:Plasmids / Q000235:genetics; D054323:Shiga-Toxigenic Escherichia coli / Q000235:genetics*
chemical_list: D000900:Anti-Bacterial Agents; D029968:Escherichia coli Proteins
keywords: antimicrobial; class 1 integron; food pathogens; microbial drug resistance; pathogenic bacteria