title: Introduction of quinolone resistant Escherichia coli to Swedish broiler population by imported breeding animals.
abstract: During recent years a rapid increase of quinolone resistant Escherichia coli have been noted in the Swedish broiler population, despite the lack of a known selective pressure. The current study wanted to investigate if imported breeding birds could be a source for the quinolone resistant E. coli. The occurrence of quinolone resistant E. coli was investigated, using selective cultivation with nalidixic acid, in grand-parent birds on arrival to Sweden and their progeny. In addition, sampling in hatcheries and empty cleaned poultry houses was performed. Clonality of isolates was investigated using a 10-loci multiple-locus variable number tandem repeat analysis (MLVA). To identify the genetic basis for the resistance isolates were also analysed for occurrence of plasmid-mediated quinolone resistance (PMQR) determinants and characterization of chromosomal mutations. E. coli resistant to nalidixic acid occurred in grandparent birds imported to Sweden for breeding purposes. Four predominant MLVA types were identified in isolates from grandparent birds, parent birds and broilers. However, resistant E. coli with identical MLVA patterns were also present in hatcheries and poultry houses suggesting that the environment plays a role in the occurrence. Nalidixic acid resistance was due to a mutation in the gyrA gene and no PMQR could be identified. The occurrence of identical clones in all levels of the production pyramid points to that quinolone resistant E. coli can be introduced through imported breeding birds and spread by vertical transmission to all levels of the broiler production pyramid.
authors.affiliation: National Veterinary Institute, Uppsala, Sweden. Electronic address: stefan.borjesson@sva.se.
authors.forename: Stefan
authors.initials: S
authors.lastname: Börjesson
authors.affiliation: CHU Reims, Hôpital Robert Debré, Laboratoire de Bactériologie-Virologie-Hygiène, F-51092 Reims, France; UFR Médecine, EA 4687 ERA, SFR CAP-Santé, Université de Reims Champagne-Ardenne, F-51092 Reims, France.
authors.forename: Thomas
authors.initials: T
authors.lastname: Guillard
authors.affiliation: National Veterinary Institute, Uppsala, Sweden.
authors.forename: Annica
authors.initials: A
authors.lastname: Landén
authors.affiliation: National Veterinary Institute, Uppsala, Sweden.
authors.forename: Björn
authors.initials: B
authors.lastname: Bengtsson
authors.affiliation: National Veterinary Institute, Uppsala, Sweden.
authors.forename: Oskar
authors.initials: O
authors.lastname: Nilsson
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001947:Breeding; D002645:Chickens; D027081:DNA Gyrase / Q000235:genetics; D024881:Drug Resistance, Bacterial / Q000235:genetics; D004783:Environmental Microbiology; D004926:Escherichia coli / Q000187:drug effects* / Q000235:genetics / Q000502:physiology*; D006799:Housing, Animal; D018598:Minisatellite Repeats / Q000235:genetics; D009154:Mutation; D015363:Quinolones / Q000494:pharmacology*; D013548:Sweden; D014186:Transportation
chemical_list: D000900:Anti-Bacterial Agents; D015363:Quinolones; D027081:DNA Gyrase
keywords: Antibiotic resistance; Broiler; Escherichia coli; Fluoroquinolone; Grandparent animals; Import; Nalidixic acid; Production pyramid; Quinolone