title: Vertical transmission of highly similar bla CTX-M-1-harboring IncI1 plasmids in Escherichia coli with different MLST types in the poultry production pyramid.
abstract: OBJECTIVE
  The purpose of this study was to characterize sets of extended-spectrum β-lactamases (ESBL)-producing Enterobacteriaceae collected longitudinally from different flocks of broiler breeders, meconium of 1-day-old broilers from theses breeder flocks, as well as from these broiler flocks before slaughter.
  
  
  METHODS
  Five sets of ESBL-producing Escherichia coli were studied by multi-locus sequence typing (MLST), phylogenetic grouping, PCR-based replicon typing and resistance profiling. The bla CTX-M-1-harboring plasmids of one set (pHV295.1, pHV114.1, and pHV292.1) were fully sequenced and subjected to comparative analysis.
  
  
  RESULTS
  Eleven different MLST sequence types (ST) were identified with ST1056 the predominant one, isolated in all five sets either on the broiler breeder or meconium level. Plasmid sequencing revealed that bla CTX-M-1 was carried by highly similar IncI1/ST3 plasmids that were 105 076 bp, 110 997 bp, and 117 269 bp in size, respectively.
  
  
  CONCLUSIONS
  The fact that genetically similar IncI1/ST3 plasmids were found in ESBL-producing E. coli of different MLST types isolated at the different levels in the broiler production pyramid provides strong evidence for a vertical transmission of these plasmids from a common source (nucleus poultry flocks).
authors.affiliation: Institute for Food Safety and Hygiene, Vetsuisse Faculty, University of Zurich Zürich, Switzerland.
authors.forename: Katrin
authors.initials: K
authors.lastname: Zurfluh
authors.affiliation: UCD Centre for Food Safety, School of Public Health, Physiotherapy and Population Science, UCD Centre for Molecular Innovation and Drug Discovery, University College Dublin Dublin, Ireland.
authors.forename: Juan
authors.initials: J
authors.lastname: Wang
authors.affiliation: Institute of Food, Nutrition and Health, Swiss Federal Institute of Technology in Zürich Zürich, Switzerland.
authors.forename: Jochen
authors.initials: J
authors.lastname: Klumpp
authors.affiliation: Institute for Food Safety and Hygiene, Vetsuisse Faculty, University of Zurich Zürich, Switzerland.
authors.forename: Magdalena
authors.initials: M
authors.lastname: Nüesch-Inderbinen
authors.affiliation: UCD Centre for Food Safety, School of Public Health, Physiotherapy and Population Science, UCD Centre for Molecular Innovation and Drug Discovery, University College Dublin Dublin, Ireland.
authors.forename: Séamus
authors.initials: S
authors.lastname: Fanning
authors.affiliation: Institute for Food Safety and Hygiene, Vetsuisse Faculty, University of Zurich Zürich, Switzerland.
authors.forename: Roger
authors.initials: R
authors.lastname: Stephan
keywords: CTX-M-1; E. coli; IncI1; conjugation; plasmid sequencing; poultry production pyramid