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Characterization of multidrug-resistant Escherichia coli isolates from animals presenting at a university veterinary

Maria Karczmarczyk1, Yvonne Abbott, Ciara Walsh

  • 1UCD Centre for Food Safety & Centre for Food-borne Zoonomics, UCD Veterinary Sciences Centre, University College Dublin, Belfield, Dublin 4, Ireland.

Applied and Environmental Microbiology
|August 23, 2011
PubMed

Insights

Multidrug resistance in Escherichia coli from Irish animals is driven by transferable genes, including concerning extended-spectrum beta-lactamases (ESBLs). This highlights the need for monitoring antimicrobial resistance in animal populations.

Area of Science:

  • Veterinary Microbiology
  • Molecular Biology
  • Antimicrobial Resistance

Background:

  • Multidrug resistance (MDR) in bacteria poses a significant threat to animal and human health.
  • Escherichia coli is a common commensal bacterium in animals and can act as a reservoir for resistance genes.
  • Understanding the genetic basis of MDR in animal-associated E. coli is crucial for effective treatment and control strategies.

Purpose of the Study:

  • To investigate the molecular mechanisms of multidrug resistance (MDR) in Escherichia coli isolates from hospitalized animals in Ireland.
  • To identify specific resistance genes, integrons, and mobile genetic elements contributing to MDR.
  • To assess the prevalence and transferability of these resistance determinants.

Main Methods:

  • Polymerase Chain Reaction (PCR) and DNA sequencing were employed to detect and identify resistance genes.
  • Class 1 and Class 2 integrons were analyzed for their gene cassette content.
  • Conjugation assays were performed to evaluate the mobility of resistance genes via plasmids.

Main Results:

  • Class 1 integrons were highly prevalent (94.6%), carrying genes conferring resistance to aminoglycosides, β-lactams, and trimethoprim.
  • Class 2 integrons (13.5%) contained the dfrA1-sat1-aadA1 gene array.
  • High levels of phenotypic resistance were observed, including to ampicillin (97.3%), sulfonamide (98.6%), and tetracycline (100%).
  • Specific resistance determinants like bla(TEM), cat, floR, aadB, aphA1, strA-strB, sul2, and tet(B) were identified.
  • The extended-spectrum β-lactamase (ESβL) gene bla(CTX-M-2) and the AmpC-like gene bla(CMY-2) were detected in 8 and 18 isolates, respectively.
  • Conjugation assays confirmed the transferability of resistance genes, primarily mediated by high-molecular-weight plasmids.
  • The bla(CTX-M-2) gene represents a novel finding in Ireland.

Conclusions:

  • Animal-associated commensal E. coli isolates harbor a diverse array of transferable genetic determinants for antimicrobial resistance.
  • The emergence and dissemination of ESBLs and AmpC-like enzymes in this context are of significant concern.
  • The findings underscore the importance of monitoring antimicrobial resistance in veterinary settings and its potential implications for public health.

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