Passive surveillance of antimicrobial resistance in <i>Salmonella</i> and <i>Escherichia coli</i> isolates from Ontario livestock, 2007-2015.

Abstract

Clinical isolates are important to antimicrobial resistance surveillance efforts because clinically ill animals are the direct targets of antimicrobial treatments. Thus, clinical data may provide a surveillance tool for identifying emerging resistance threats. The purpose of this study was to describe resistance trends in <i>Escherichia coli</i> and <i>Salmonella</i> spp. from clinically ill animals over time and evaluate the utility of these laboratory data as a passive surveillance tool. Susceptibility results of isolates from chickens, swine, and cattle recovered between 2007 and 2015 at a major veterinary diagnostic laboratory in Ontario, Canada were analyzed. Relative to other antimicrobials tested, visible trends highlighted high resistance to ampicillin and tetracycline in chicken <i>E. coli,</i> consistently high resistance to tetracycline, sulfisoxazole, and ampicillin among swine isolates, and an increase in cattle <i>E. coli</i> resistant to ampicillin and cephalothin over time. While the data show potential for use in surveillance, there are limitations of such a clinical dataset for predicting overall trends and guiding empirical treatment decisions.