Strain Diversity of CTX-M-Producing Enterobacteriaceae in Individual Pigs: Insights into the Dynamics of Shedding during the Production Cycle: insights into the dynamics of shedding during the production cycle

Katrine Hartung Hansen, Valeria Bortolaia, Peter Damborg, Luca Guardabassi, H. Goodrich-Blair (Editor)

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The aim of this study was to evaluate the population dynamics of CTX-M-producing Enterobacteriaceae in individual pigs on a farm positive for CTX-M-14-producing Escherichia coli. Fecal samples were collected once around the farrowing time from five sows and four times along the production cycle from two of their respective offspring. Multiple colonies per sample were isolated on cefotaxime-supplemented MacConkey agar with or without prior enrichment, resulting in 98 isolates identified by matrix-assisted laser desorption ionization-time of flight mass spectrometry and tested for bla(CTX-M). CTX-M-positive isolates (n = 86) were typed by pulsed-field gel electrophoresis (PFGE). Plasmids harboring bla(CTX-M) were characterized in 22 representative isolates by replicon typing and restriction fragment length polymorphism. Based on the PFGE results, all individuals shed unrelated CTX-M-14-producing E. coli strains during the course of life. Concomitant shedding of CTX-M-2/97-producing Proteus mirabilis or Providencia rettgeri was observed in two sows and two offspring. At least two genetically unrelated CTX-M-producing E. coli strains were isolated from approximately one-fourth of the samples, with remarkable differences between isolates obtained by enrichment and direct plating. A clear decrease in strain diversity was observed after weaning. Dissemination of bla(CTX-M-14) within the farm was attributed to horizontal transfer of an IncK plasmid that did not carry additional resistance genes and persisted in the absence of antimicrobial selective pressure. Assessment of strain diversity was shown to be influenced by the production stage from which samples were collected, as well as by the isolation method, providing useful information for the design and interpretation of future epidemiological studies of CTX-M-producing Enterobacteriaceae in pig farms.
Original languageEnglish
JournalApplied and Environmental Microbiology
Issue number21
Pages (from-to)6620-6626
Number of pages7
Publication statusPublished - 2014
Externally publishedYes


  • Applied Microbiology and Biotechnology
  • Food Science
  • Biotechnology
  • Ecology
  • Medicine (all)
  • Electrophoresis
  • Escherichia coli
  • Mammals
  • Mass spectrometry
  • Additional resistances
  • Epidemiological studies
  • Horizontal transfer
  • Matrix-assisted laser desorption ionization
  • Pulsed field gel electrophoresis
  • Restriction fragment length polymorphisms
  • Selective pressure
  • Time of flight mass spectrometry
  • Strain
  • colony structure
  • feces
  • genetic variation
  • livestock farming
  • microbial activity
  • pig
  • plasmid
  • sampling
  • Enterobacteriaceae
  • Suidae
  • bacterial DNA
  • beta lactamase
  • beta-lactamase CTX-M-14
  • animal
  • biodiversity
  • chemistry
  • classification
  • DNA sequence
  • enzymology
  • genetics
  • horizontal gene transfer
  • isolation and purification
  • mass spectrometry
  • microbiology
  • molecular genetics
  • pulsed field gel electrophoresis
  • secretion (process)
  • Animals
  • beta-Lactamases
  • Biodiversity
  • DNA, Bacterial
  • Electrophoresis, Gel, Pulsed-Field
  • Feces
  • Gene Transfer, Horizontal
  • Molecular Sequence Data
  • Plasmids
  • Sequence Analysis, DNA
  • Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
  • Swine
  • Environmental Microbiology
  • Genetics - General
  • Genetics - Animal
  • Ecology: environmental biology - General and methods
  • Ecology: environmental biology - Animal
  • Biochemistry studies - General
  • Biochemistry studies - Nucleic acids, purines and pyrimidines
  • Bacteriology, general and systematic
  • Physiology and biochemistry of bacteria
  • Genetics of bacteria and viruses
  • cefotaxime
  • Bacteria, Eubacteria, Microorganisms
  • Animals, Artiodactyls, Chordates, Mammals, Nonhuman Vertebrates, Nonhuman Mammals, Vertebrates
  • production cycle


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