Comparison of antimicrobial resistance patterns of Salmonella spp. and Escherichia coli recovered from pet dogs from volunteer households in Ontario (2005-06)

Abstract

Objectives: To compare the antimicrobial resistance (AMR) patterns of Salmonella spp. and Escherichia coli in the faeces of pet dogs from volunteer households in Southwestern Ontario, Canada.

Methods: From October 2005 to May 2006, 138 dogs from 84 Ontario households were recruited to participate in a cross-sectional study. Five consecutive daily faecal samples were collected from each dog and cultured for Salmonella spp. and E. coli. A panel of 15 antimicrobials from seven antimicrobial classes was used for susceptibility testing.

Results: E. coli and Salmonella spp. were recovered from 96.4% and 23.2% of dogs, respectively. In total, 515 bacterial isolates from 136 dogs from 83 households were sent for antimicrobial susceptibility testing with 80.4% of isolates being pan-susceptible. The most common resistance pattern was to amoxicillin/clavulanic acid, ampicillin, cefoxitin, ceftiofur and ceftriaxone, present in 13.3% of Salmonella isolates and 1.3% of E. coli isolates. Fifty-eight of the isolates were resistant to two or more drug classes, with 70.7% and 29.3% being E. coli and Salmonella, respectively. Based on multilevel logistic regression, the odds of resistance were greater in E. coli than Salmonella [odds ratio = 3.2; 95% confidence interval (CI) = 1.22-8.43]. Agreement in resistance between E. coli and Salmonella isolates from the same dog was low [prevalence-adjusted, bias-adjusted kappa (PABAK) = 0.38; 95% CI = 0.30-0.46].

Conclusions: Pet dogs are a potential household source of antimicrobial-resistant Salmonella spp. and E. coli. However, extrapolating the epidemiology of antimicrobial resistance in pathogens, like Salmonella, from E. coli should be done with caution.