title: Vertical transmission of Escherichia coli carrying plasmid-mediated AmpC (pAmpC) through the broiler production pyramid.
abstract: OBJECTIVE
  In Sweden the prevalence of Enterobacteriaceae with transferable resistance to extended-spectrum cephalosporins (ESCs) is low. However, in broilers ESC-resistant Escherichia coli is common, with a clear dominance of blaCMY-2. Antimicrobials are rarely used in broiler production in Sweden and cephalosporins are never used. Introduction through imported breeding stock and subsequent vertical transmission of the bacteria through the production pyramid could be one explanation for this high prevalence.
  
  
  METHODS
  To test this hypothesis, paper linings from imported flocks of grandparent animals were screened for the presence of ESC-resistant E. coli and a positive flock, together with its progeny, was followed longitudinally through the production pyramid using boot swabs. The relationship of isolated ESC-resistant E. coli was investigated using multiple-locus variable number tandem repeat analysis (MLVA).
  
  
  RESULTS
  ESC-resistant E. coli carrying blaCMY-2 was isolated from six out of eight imported flocks of grandparent animals. One clone of E. coli carrying blaCMY-2 occurred in all levels of the production pyramid and in flocks of imported grandparent animals.
  
  
  CONCLUSIONS
  E. coli carrying blaCMY-2 is frequently present among grandparent animals imported to Sweden for breeding purposes. The occurrence of one clone in all levels of the production pyramid indicates that its introduction through imported breeding stock and vertical transmission through the production pyramid could be one explanation for the high proportion of Swedish broilers colonized with ESC-resistant E. coli.
authors.affiliation: Department of Animal Health and Antimicrobial Strategies, National Veterinary Institute, SE-751 89 Uppsala, Sweden.
authors.forename: Oskar
authors.initials: O
authors.lastname: Nilsson
authors.affiliation: Department of Animal Health and Antimicrobial Strategies, National Veterinary Institute, SE-751 89 Uppsala, Sweden stefan.borjesson@sva.se.
authors.forename: Stefan
authors.initials: S
authors.lastname: Börjesson
authors.affiliation: Department of Animal Health and Antimicrobial Strategies, National Veterinary Institute, SE-751 89 Uppsala, Sweden.
authors.forename: Annica
authors.initials: A
authors.lastname: Landén
authors.affiliation: Department of Animal Health and Antimicrobial Strategies, National Veterinary Institute, SE-751 89 Uppsala, Sweden.
authors.forename: Björn
authors.initials: B
authors.lastname: Bengtsson
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics*; D018550:Cephalosporin Resistance / Q000235:genetics; D002645:Chickens; D004926:Escherichia coli / Q000145:classification / Q000235:genetics*; D004927:Escherichia coli Infections / Q000382:microbiology* / Q000635:transmission*; D018445:Infectious Disease Transmission, Vertical; D058885:Multilocus Sequence Typing; D010957:Plasmids / Q000235:genetics*; D011201:Poultry Diseases / Q000382:microbiology / Q000635:transmission; D013548:Sweden; D001618:beta-Lactamases / Q000235:genetics*
chemical_list: D001426:Bacterial Proteins; C048795:AmpC beta-lactamases; D001618:beta-Lactamases
keywords: ESBL; blaCMY-2; resistance