title: Within-farm dynamics of ESBL/AmpC-producing Escherichia coli in veal calves: a longitudinal approach.
abstract: OBJECTIVE
  To assess the within-farm dynamics of extended-spectrum β-lactamase (ESBL)/AmpC-producing Escherichia coli in veal calves.
  
  
  METHODS
  Three veal-calf fattening farms were screened. Faecal samples from all calves within a compartment (109-150 per farm) were taken upon arrival on the farm (T0) and after 3, 6, 8 and 10 weeks (T3-T10). ESBL/AmpC genes were characterized by PCR and sequencing. Plasmids were characterized by transformation, PCR-based replicon typing and plasmid multilocus sequence typing (MLST). E. coli genotypes were analysed by MLST.
  
  
  RESULTS
  At T0 the prevalence of ESBL/AmpC-producing E. coli ranged from 18% to 26%. These were predominantly isolates carrying blaCTX-M-1 and blaCTX-M-15 genes, located on various plasmids and E. coli sequence types (STs). Farm 1 was negative for ESBL/AmpC-producing E. coli after T0. Farm 2 showed an increase up to 37% at T3, which subsequently decreased gradually to 0% at T10. The presence from T3 to T10 on farm 2 was mainly caused by the clonal spread of a multiresistant E. coli ST57 harbouring blaCTX-M-14 on an IncF F2:A-:B- plasmid. Farm 3 showed a gradual decrease in prevalence to 1.4% at T10, with a relative increase of the identical clonal variant as shown for farm 2. A second clonal variant found in farm 3 was a multiresistant E. coli ST10 harbouring blaCTX-M-14 on an IncK plasmid.
  
  
  CONCLUSIONS
  The prevalence of ESBL/AmpC-producing E. coli decreased over time. A clonal spread was observed on farm 2 and farm 3, illustrative of the complex dynamics probably associated with the use of antimicrobials.
authors.affiliation: Department of Infectious Diseases and Immunology, Faculty of Veterinary Medicine, Utrecht University, PO Box 80.165, 3508 TD Utrecht, The Netherlands.
authors.forename: Joost
authors.initials: J
authors.lastname: Hordijk
authors.forename: Dik J
authors.initials: DJ
authors.lastname: Mevius
authors.forename: Arie
authors.initials: A
authors.lastname: Kant
authors.forename: Marian E H
authors.initials: ME
authors.lastname: Bos
authors.forename: Haitske
authors.initials: H
authors.lastname: Graveland
authors.forename: Angela B
authors.initials: AB
authors.lastname: Bosman
authors.forename: Cedric M
authors.initials: CM
authors.lastname: Hartskeerl
authors.forename: Dick J J
authors.initials: DJ
authors.lastname: Heederik
authors.forename: Jaap A
authors.initials: JA
authors.lastname: Wagenaar
mesh_terms: D000818:Animals; D000829:Animals, Domestic; D002417:Cattle; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004926:Escherichia coli / Q000145:classification / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification*; D004927:Escherichia coli Infections / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary*; D005243:Feces / Q000382:microbiology*; D005838:Genotype; D017720:Molecular Epidemiology; D058885:Multilocus Sequence Typing; D010957:Plasmids / Q000032:analysis; D016133:Polymerase Chain Reaction; D015995:Prevalence; D014169:Transformation, Bacterial; D001618:beta-Lactamases / Q000235:genetics / Q000378:metabolism*
chemical_list: D004269:DNA, Bacterial; D001618:beta-Lactamases
keywords: antimicrobial resistance; cattle; faecal carriage