Poster Presentation Australian Society for Microbiology Annual Scientific Meeting 2013

Multidrug resistance in phylogenetic group D fluoroquinolone-resistant extraintestinal pathogenic Escherichia coli in Australian dogs. (#268)

David L Wakeham 1 , Sam Abraham 1 , SiYu Guo 2 , Joanne Platell 3 , Darren J Trott 1
  1. School of Animal and Veterinary Sciences, University of Adelaide, Roseworthy, SA, Australia
  2. New South Wales Department of Primary Industries, Wollongbar, NSW, Australia
  3. Biosecurity Sciences Laboratory, Department of Agriculture and Fisheries, Brisbane, QLD, Australia

Extraintestinal pathogenic Escherichia coli (ExPEC) strains are an important cause of urinary tract infections in humans and companion animals. Whilst a growing body of evidence shows a strong commonality of phylogenetic group B2 ExPEC strains isolated from humans and dogs, little work has been conducted on group D isolates. Group D ExPEC isolates are far more prevalent in dogs than B2 groups. This study aimed to identify the degree of multidrug resistance (sensitive to ≥1 agent in ≥3 antimicrobial categories) in fluoroquinolone-resistant (FQr) group D ExPEC strains from dogs in Australia.  A collection of FQr group D ExPEC from canine faeces (n=27) and clinical extraintestinal infections (n=38) were subjected to CLSI disc diffusion for 16 antimicrobials of importance to veterinary and public health. All faecal and 97.4% of the clinical isolates exhibited a MDR phenotype. All isolates were resistant to cephalothin, while a high frequency of resistance was observed to ampicillin (faecal 88.9%; clinical 91.9%), gentamicin (faecal 85.2%; clinical 43.2%) and tetracycline (faecal 43.2%; clinical 89.2%). Varying levels of resistance to 2nd and 3rd generation cephalosporins were observed. Amongst the clinical isolates; only 10.5 % were resistant to cefoxitin while 21.1% were resistant to ceftazidime, 26.3% were resistant to ceftiofur and 31.6% were resistant to cefovecin. Amongst the faecal isolates, however, none were resistant to cefoxitin or ceftazidime, yet 33.3% were resistant to ceftiofur and cefovecin. Only one of the clinical isolates showed intermediate resistance to imipenem. These differences in resistance between the different generations of human and veterinary cephalosporins may indicate the presence of multiple extended-spectrum β-lactamases in some of the isolates. Although further study is required to investigate the array of extended-spectrum β-lactamases in these isolates, the results confirm that canine faeces are a reservoir for MDR phylogenetic group D ExPEC.