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Reservoirs of resistance: polymyxin resistance in veterinary-associated companion animal isolates of Pseudomonas aeruginosa
  1. Andrea Scott1,
  2. Sian Pottenger1,
  3. Dorina Timofte2,
  4. Matthew Moore1,
  5. Laura Wright1,
  6. Irena Kukavica-Ibrulj3,
  7. Julie Jeukens3,
  8. Roger C Levesque3,
  9. Luca Freschi3,
  10. Gina L Pinchbeck1,
  11. Vanessa M Schmidt1,2,
  12. Neil McEwan2,
  13. Alan D Radford1 and
  14. Joanne L Fothergill1
  1. 1 Institute of Infection and Global Health, University of Liverpool, Liverpool, UK
  2. 2 Institute of Veterinary Science, University of Liverpool, Neston, Wirral, UK
  3. 3 Université Laval, Quebec City, Quebec, Canada
  1. E-mail for correspondence; j.fothergill{at}, jofoth{at}


Background Pseudomonas aeruginosa is an opportunistic pathogen and a major cause of infections. Widespread resistance in human infections are increasing the use of last resort antimicrobials such as polymyxins. However, these have been used for decades in veterinary medicine. Companion animals are an understudied source of antimicrobial resistant P. aeruginosa isolates. This study evaluated the susceptibility of P. aeruginosa veterinary isolates to polymyxins to determine whether the veterinary niche represents a potential reservoir of resistance genes for pathogenic bacteria in both animals and humans.

Methods and results Clinical P. aeruginosa isolates (n=24) from UK companion animals were compared for antimicrobial susceptibility to a panel of human-associated isolates (n=37). Minimum inhibitory concentration (MIC) values for polymyxin B and colistin in the companion animals was significantly higher than in human isolates (P=0.033 and P=0.013, respectively). Genotyping revealed that the veterinary isolates were spread throughout the P. aeruginosa population, with shared array types from human infections such as keratitis and respiratory infections, suggesting the potential for zoonotic transmission. Whole genome sequencing revealed mutations in genes associated with polymyxin resistance and other antimicrobial resistance-related genes.

Conclusion The high levels of resistance to polymyxin shown here, along with genetic similarities between some human and animal isolates, together suggest a need for sustained surveillance of this veterinary niche as a potential reservoir for resistant, clinically relevant bacteria in both animals and humans.

  • antimicrobials
  • bacteriology
  • bacterial pathogenesis
  • infection
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  • AS and SP contributed equally.

  • Funding The work was supported by a University of Liverpool/Wellcome Trust Research taster fellowship and internal funding. AS is supported by a University of Liverpool/Wellcome Trust Research taster fellowship and JLF is supported by a Leverhulme Trust Early Career Fellowship. JJ is supported by a Cystic Fibrosis Canada postdoctoral fellowship. RCL is funded by Cystic Fibrosis Canada and by the Canadian Institute for Health Research (CIHR).

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data sharing statement Data are available in a public, open access repository.

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