The Emergence of Broad-Spectrum ß-Lactamases in E. coli from Canine Urinary Tract Infections in Western Canada

Antimicrobial resistance is a serious threat to modern medicine. Broad-spectrum ß-lactamase producing Escherichia coli resistant to the 3^rd generation cephalosporins (3GC), are among the most notorious superbugs. These ß-lactamases, including the CTX-M and AmpC type enzymes, are frequently co-located on plasmids with other resistance genes facilitating the selection of multidrug resistance. Because, E. coli is the most common cause of canine urinary tract infections, this organism is a rational target for resistance surveillance. The objective of this study was to describe the emergence of broad spectrum ß-lactamases, and changes in the susceptibility of E. coli causing canine urinary tract infections over 3 years beginning in October, 2013. A total of 292 isolates recovered by a regional diagnostic laboratory in Saskatoon, Canada were included. The susceptibility of isolates to a broad panel of drugs including the 3GC ceftriaxone and ceftiofur was determined, and 3GC resistant isolates were screened for ß-lactamase genes by PCR. The frequency of resistance increased significantly over the study period. Multidrug resistance (resistance to 3 or more drug classes) increased from 4.6% of isolates collected in year 1 to 15.8% in year 3 (P = 0.009). Resistance to 3GC also increased; the proportion of isolates producing CMY-2 increased from 0.9% (year 1) to 4.2% (year 3), while CTX-M producers increased from 0% (year 1) to 2.1% (year 3). Continued work is required to understand the epidemiology of resistance, and provide veterinarians with the information required to make evidence based empiric treatment decisions.