Dissemination of cephalosporin resistance genes between Escherichia coli strains from farm animals and humans by specific plasmid lineages

Research output: Contribution to journalArticle


  • Mark de Been
  • Val F Lanza
  • María de Toro
  • Jelle Scharringa
  • Wietske Dohmen
  • Yu Du
  • Juan Hu
  • Ying Lei
  • Ning Li
  • Ave Tooming-Klunderud
  • Dick J J Heederik
  • Ad C Fluit
  • Marc J M Bonten
  • Rob J L Willems
  • Fernando de la Cruz

Colleges, School and Institutes

External organisations

  • Department of Medical Microbiology, University Medical Center Utrecht, Utrecht, The Netherlands
  • Instituto de Biomedicina y Biotecnología de Cantabria, Universidad de Cantabria-Sodercan-CSIC, Santander, Spain.
  • Institute for Risk Assessment Sciences, Division of Environmental Epidemiology, Utrecht University, Utrecht, The Netherlands.
  • BGI-Shenzhen, Shenzhen, China.
  • BGI-Europe, Copenhagen, Denmark.
  • Norwegian High-Throughput Sequencing Centre, Centre for Ecological and Evolutionary Synthesis, Department of Biosciences, University of Oslo, Oslo, Norway.


Third-generation cephalosporins are a class of β-lactam antibiotics that are often used for the treatment of human infections caused by Gram-negative bacteria, especially Escherichia coli. Worryingly, the incidence of human infections caused by third-generation cephalosporin-resistant E. coli is increasing worldwide. Recent studies have suggested that these E. coli strains, and their antibiotic resistance genes, can spread from food-producing animals, via the food-chain, to humans. However, these studies used traditional typing methods, which may not have provided sufficient resolution to reliably assess the relatedness of these strains. We therefore used whole-genome sequencing (WGS) to study the relatedness of cephalosporin-resistant E. coli from humans, chicken meat, poultry and pigs. One strain collection included pairs of human and poultry-associated strains that had previously been considered to be identical based on Multi-Locus Sequence Typing, plasmid typing and antibiotic resistance gene sequencing. The second collection included isolates from farmers and their pigs. WGS analysis revealed considerable heterogeneity between human and poultry-associated isolates. The most closely related pairs of strains from both sources carried 1263 Single-Nucleotide Polymorphisms (SNPs) per Mbp core genome. In contrast, epidemiologically linked strains from humans and pigs differed by only 1.8 SNPs per Mbp core genome. WGS-based plasmid reconstructions revealed three distinct plasmid lineages (IncI1- and IncK-type) that carried cephalosporin resistance genes of the Extended-Spectrum Beta-Lactamase (ESBL)- and AmpC-types. The plasmid backbones within each lineage were virtually identical and were shared by genetically unrelated human and animal isolates. Plasmid reconstructions from short-read sequencing data were validated by long-read DNA sequencing for two strains. Our findings failed to demonstrate evidence for recent clonal transmission of cephalosporin-resistant E. coli strains from poultry to humans, as has been suggested based on traditional, low-resolution typing methods. Instead, our data suggest that cephalosporin resistance genes are mainly disseminated in animals and humans via distinct plasmids.


Original languageEnglish
Article numbere1004776
Number of pages17
JournalPLoS Genetics
Issue number12
Publication statusPublished - 18 Dec 2014


  • Animals, Anti-Bacterial Agents, Cephalosporin Resistance, Chickens, DNA, Bacterial, Escherichia coli, Escherichia coli Infections, Food Contamination, Food Microbiology, Meat, Phylogeny, Plasmids, Polymorphism, Single Nucleotide, Sequence Analysis, DNA, Swine, Journal Article, Research Support, Non-U.S. Gov't