Distribution and possible transmission of ampicillin- and nalidixic acid-resistant Escherichia coli within the broiler industry

Valeria Bortolaia, Magne Bisgaard, Anders Miki Bojesen

Research output: Contribution to journalJournal articleResearchpeer-review


This study was performed to determine the origin and transmission of beta-lactam- and (fluoro)quinolone-resistant Escherichia coli in healthy, untreated broiler flocks. We focused on the dynamics of bacteria resistant to critically important antimicrobials for public and veterinary health in view of the possible link between antimicrobial resistant bacteria in farm animals and humans. By processing faecal samples collected with the sock method in broiler parent and broiler flocks, E. coli resistant to ampicillin and nalidixic acid were frequently isolated, while resistance to ciprofloxacin was detected at a very low frequency, and resistance to cephalosporins was not detected. Similarly, resistance to ampicillin and nalidixic acid were the only phenotypes detected in a collection of clinical E. coli isolates associated with first-week-mortality in broiler parent chicks. Although antimicrobial resistant E. coli were genetically diverse by means of amplified fragment length polymorphism (AFLP) typing, indistinguishable isolates were present in different flocks, including isolates from broiler parent chicks, broiler parents and broilers. In the absence of apparent selective pressure, the genotypic heterogeneity that we describe is likely the consequence of multiple introductions of antimicrobial resistant bacteria into the production system. The confinement under which broilers are raised limits the possibilities of bacterial transmission among different flocks. Our findings are consistent with vertical transmission of ampicillin- and nalidixic acid-resistant E. coli through the broiler production system. The persistence of antimicrobial resistant E. coli in healthy, untreated chicken flocks emphasises the need of careful evaluation of therapeutic options at any level of the broiler production. (C) 2009 Elsevier B.V. All rights reserved.
Original languageEnglish
JournalVeterinary Microbiology
Issue number3-4
Pages (from-to)379-386
Number of pages8
Publication statusPublished - 2010
Externally publishedYes


  • LIFE
  • Escherichia coli
  • antimicrobial resistance
  • Poultry
  • Vertical transmission
  • AFLP
  • Microbiology
  • Veterinary (all)
  • Antimicrobial resistance
  • ampicillin
  • beta lactam antibiotic
  • cefotaxime
  • ceftiofur
  • cephalosporin derivative
  • ciprofloxacin
  • nalidixic acid
  • quinoline derived antiinfective agent
  • amplified fragment length polymorphism
  • antibiotic resistance
  • article
  • bacterial transmission
  • bacterium isolation
  • broiler
  • chicken
  • controlled study
  • feces analysis
  • genetic heterogeneity
  • genetic selection
  • genotype
  • minimum inhibitory concentration
  • mortality
  • nonhuman
  • phenotype
  • poultry farming
  • vertical transmission
  • veterinary medicine
  • Ampicillin
  • Ampicillin Resistance
  • Amplified Fragment Length Polymorphism Analysis
  • Animals
  • Anti-Bacterial Agents
  • Chickens
  • Drug Resistance, Bacterial
  • Escherichia coli Infections
  • Feces
  • Genotype
  • Microbial Sensitivity Tests
  • Nalidixic Acid
  • Phenotype
  • Poultry Diseases
  • Animalia
  • Bacteria (microorganisms)
  • PIGS
  • Biochemistry studies - General
  • Pathology - Therapy
  • Pharmacology - General
  • Physiology and biochemistry of bacteria
  • Medical and clinical microbiology - General and methods
  • Medical and clinical microbiology - Bacteriology
  • Chemotherapy - General, methods and metabolism
  • Chemotherapy - Antibacterial agents
  • cephalosporin
  • Bacteria, Eubacteria, Microorganisms
  • Animals, Birds, Chordates, Nonhuman Vertebrates, Vertebrates


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