title: Molecular characterization of Irish E. coli O157:H7 isolates of human, bovine, ovine and porcine origin.
abstract: OBJECTIVE
  To determine the degree of relatedness between isolates of Escherichia coli O157:H7 of human, bovine, ovine and porcine origin.
  
  
  RESULTS
  Escherichia coli O157:H7 isolates were compared using (i) PFGE XbaI patterns, (ii) PCR profiles of virulence genes and (iii) the DNA sequences of genes reported to play a role in pathogenicity. The 77 E. coli O157:H7 isolates demonstrated 49 different PFGE patterns of which, eight were common to multiple isolates, and the remaining 41 were distinct. Isolates of different origin did not correlate, except for one cluster consisting of two human and two beef isolates. The majority of animal isolates had the same PCR profiles of virulence genes as those isolated from clinical patients. Single nucleotide polymorphisms (SNPs) were identified in the sequence of a 255-bp region of the vtx2 subunit A gene.
  
  
  CONCLUSIONS
  Six SNPs were detected in the vtx2A gene, defining four different haplotypes. One nonsynonymous substitution encoded for an amino acid change from glutamic to aspartic acid.
  
  
  CONCLUSIONS
  Results indicate that although E. coli O157:H7 isolates of differing origin were distinct by PFGE, the DNA sequences of the main virulence genes associated with human clinical illness were conserved.
authors.affiliation: Teagasc, Ashtown Food Research Centre, Ashtown, Dublin 15, Ireland. mary.lenahan@teagasc.ie
authors.forename: M
authors.initials: M
authors.lastname: Lenahan
authors.forename: S B
authors.initials: SB
authors.lastname: O'Brien
authors.forename: C
authors.initials: C
authors.lastname: Byrne
authors.forename: M
authors.initials: M
authors.lastname: Ryan
authors.forename: C-A
authors.initials: CA
authors.lastname: Kennedy
authors.forename: E B
authors.initials: EB
authors.lastname: McNamara
authors.forename: S
authors.initials: S
authors.lastname: Fanning
authors.forename: J J
authors.initials: JJ
authors.lastname: Sheridan
authors.forename: T
authors.initials: T
authors.lastname: Sweeney
mesh_terms: D000818:Animals; D002417:Cattle / Q000382:microbiology*; D004269:DNA, Bacterial / Q000235:genetics; D016521:Electrophoresis, Gel, Pulsed-Field; D004927:Escherichia coli Infections / Q000382:microbiology*; D019453:Escherichia coli O157 / Q000235:genetics / Q000302:isolation & purification* / Q000472:pathogenicity; D029968:Escherichia coli Proteins / Q000235:genetics; D005243:Feces / Q000382:microbiology; D006801:Humans; D016133:Polymerase Chain Reaction / Q000379:methods; D020641:Polymorphism, Single Nucleotide; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D034561:Sheep, Domestic / Q000382:microbiology*; D013552:Swine / Q000382:microbiology*; D014774:Virulence / Q000235:genetics
chemical_list: D004269:DNA, Bacterial; D029968:Escherichia coli Proteins