title: Antibiotic resistance and molecular epidemiology of Escherichia coli O26, O103 and O145 shed by two cohorts of Scottish beef cattle.
abstract: OBJECTIVE
  The aim of this study was to identify the profile of antibiotic resistance among E. coli O26, O103 and O145 in two cohorts of Scottish beef cattle on two farms and to determine whether there is an association between resistant phenotypes and the genotypic PFGE patterns to suggest clonality among resistant strains.
  
  
  METHODS
  MICs of 11 antibiotics for 297 E. coli O26, 152 E. coli O103 and 13 E. coli O145 were determined. Isolates were screened for the presence integrons 1 and 2 and the virulence factors stx1, stx2, eaeA and ehxA by PCR with specific primers. PFGE subtyping was performed after digestion with XbaI endonuclease.
  
  
  RESULTS
  Among E. coli O26, O103 and O145 there were four, four and one isolates, respectively, that harboured a class 1 integron. A class 2 integron was detected in only one O145 isolate. Diversity in PFGE patterns was higher among E. coli O103 and O145 strains compared with the O26 serotype; and PFGE demonstrated 13, 27 and 6 different patterns among O26, O103 and O145 isolates, respectively. Selective PFGE types that harboured virulence factors were widespread among the cattle population throughout the sampling period. There were multiply resistant isolates that were of similar PFGE patterns.
  
  
  CONCLUSIONS
  The dissemination and persistence of certain PFGE genotypes among the cattle population was evident in this study. Certain resistance phenotypes, especially among E. coli O26 isolates, were associated with distinct PFGE clones.
authors.affiliation: Molecular Chemotherapy, Centre for Infectious Diseases, The Chancellor's Building, 49 Little France Crescent, University of Edinburgh, Edinburgh EH16 4SB, UK.
authors.forename: Leila
authors.initials: L
authors.lastname: Vali
authors.forename: Ahmed
authors.initials: A
authors.lastname: Hamouda
authors.forename: Deborah V
authors.initials: DV
authors.lastname: Hoyle
authors.forename: Michael C
authors.initials: MC
authors.lastname: Pearce
authors.forename: Lucy H R
authors.initials: LH
authors.lastname: Whitaker
authors.forename: Claire
authors.initials: C
authors.lastname: Jenkins
authors.forename: Hazel I
authors.initials: HI
authors.lastname: Knight
authors.forename: Alastair W
authors.initials: AW
authors.lastname: Smith
authors.forename: Sebastian G B
authors.initials: SG
authors.lastname: Amyes
mesh_terms: D000818:Animals; D002417:Cattle / Q000382:microbiology*; D015331:Cohort Studies; D024881:Drug Resistance, Bacterial; D016521:Electrophoresis, Gel, Pulsed-Field; D004926:Escherichia coli / Q000187:drug effects* / Q000235:genetics; D032023:Integrons; D008826:Microbial Sensitivity Tests