Antimicrobial resistance profiles and clonal relatedness of canine and feline Escherichia coli pathogens expressing multidrug resistance in the United States

J Vet Intern Med. Mar-Apr 2010;24(2):323-30. doi: 10.1111/j.1939-1676.2009.0468.x.


Background: Antimicrobial resistance is increasing among Escherichia coli isolates associated with spontaneous infection in dogs and cats.

Objectives: To describe E. coli resistance phenotypes and clonal relatedness and their regional prevalence.

Animals: Isolates of E. coli (n = 376) collected from dogs and cats in the United States between May and September 2005.

Methods: Isolates submitted from the South, West, Northeast, and Midwest regions of the United States were prospectively studied. Phenotype was based on E-test susceptibility to 7 antimicrobials. Isolates were classified as no (NDR), single (SDR), or multidrug resistance (MDR). Clonal relatedness was determined by pulsed-field gel electrophoresis (PFGE).

Results: One hundred and ninety-three (51%) isolates expressed resistance to at least 1 drug, yielding 42 phenotypes. SDR isolates (n = 84; 44%, 8 phenotypes), expressed resistance most commonly to amoxicillin (30%, n = 25) and least commonly to cefpodoxime (1%, n = 1). MDR isolates (n = 109; 56%, 31 phenotypes) were resistant to amoxicillin (96%, n = 105), amoxicillin-clavulanate (85%, n = 93), and enrofloxacin (64%, n = 70); 18% (n = 20) were resistant to all drugs tested. The frequency of MDR did not differ regionally (P = .066). MDR minimum inhibitory concentrations (MICs) were 6-fold higher than SDR MICs (P < .0001). Dendrograms of 91 isolates representing 25 phenotypes revealed 62 different PFGE profiles.

Conclusions and clinical importance: E. coli strains spontaneously infecting dogs and cats are genetically and phenotypically diverse. Given the current prevalence of MDR among clinical isolates of E. coli in United States, implementation of a robust surveillance program is warranted.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Anti-Bacterial Agents / pharmacology*
  • Cat Diseases / epidemiology
  • Cat Diseases / microbiology*
  • Cats
  • Dog Diseases / epidemiology
  • Dog Diseases / microbiology*
  • Dogs
  • Drug Resistance, Multiple, Bacterial*
  • Electrophoresis, Gel, Pulsed-Field
  • Escherichia coli / drug effects*
  • Escherichia coli / genetics
  • Escherichia coli Infections / epidemiology
  • Escherichia coli Infections / microbiology
  • Escherichia coli Infections / veterinary*
  • United States / epidemiology


  • Anti-Bacterial Agents