Poultry has been identified as a reservoir of foodborne enteric pathogens and antimicrobial resistant bacteria. The objective of this study was to describe and compare antimicrobial resistant isolates from an Ontario broiler chicken farm-level baseline project (2003 to 2004) to the Canadian Integrated Program for Antimicrobial Resistance Surveillance (CIPARS) Ontario abattoir and retail surveillance data from 2003, and to the most recent (2015) CIPARS Ontario chicken surveillance data in order to assess the impact of an industry-wide policy change in antimicrobial use. Ceftiofur resistance (TIO-R) prevalence in Salmonella decreased by 7% on farm between 2003 and 2004 and 2015. During the same timeframe, TIO-R E. coli prevalence decreased significantly by 16%, 11%, and 8% in farm, abattoir, and retail samples, respectively. Gentamicin resistant (GEN-R) E. coli, however, increased by 10% in farm and 15% in retail-derived isolates, and trimethoprim-sulfamethoxazole resistant (TMSm-R) E. coli increased significantly by 20%, 18%, and 5% in farm, abattoir, and retail isolates, respectively. Similarly, ciprofloxacin-resistant (CIP-R) Campylobacter spp. significantly increased in retail isolates by 11% and increased in farm (33%) and abattoir isolates (7%). The decrease in TIO-R Salmonella/E. coli in recent years is consistent with the timing of an industry-led intervention eliminating the preventive use of ceftiofur, a third generation cephalosporin and class of antimicrobials deemed critically important to human medicine. The rise in GEN-R and TMSm-R prevalence is indicative of recent shifts in antimicrobial use. Our study highlights the importance of integrated surveillance in detecting emerging trends and determining the efficacy of interventions to improve food safety.

Clinically healthy pigs used in research are assumed to have normal cardiac structure and function. Subclinical cardiac abnormalities may adversely affect the responses being measured in these experiments. The gross and histologic lesions observed in hearts collected from a Canadian abattoir between 2012 and 2015 indicated an unexpectedly high prevalence of cardiac abnormalities: 75% (297/396) of the hearts examined had such lesions. The ratios of total heart weight to body weight and of right ventricle weight to body weight were significantly greater for the hearts with lesions than for the hearts with no lesions, which suggests that cardiac remodeling, particularly hypertrophy, had occurred. The large percentage of hearts with cardiac remodeling from asymptomatic market pigs demonstrates an increased probability that subclinical cardiac abnormalities may exist in research pigs, especially those accessed through commercial channels. Researchers should be aware of this likelihood if subclinical cardiac abnormalities could adversely affect their experimental findings.

Colistin is one of the last-resort antibiotics for the treatment of multidrug-resistant infections in humans, but transmissible colistin-resistance genes have emerged in bacteria from animals. The rapid and sensitive detection among animals of colonization with bacteria carrying these genes is critical in helping to control further spread. Here we describe a method for broth enrichment of colistin-resistant Escherichia coli from animal fecal and cecal samples followed by real-time polymerase chain reaction (PCR) for the simultaneous detection of two of the main colistin-resistance genes, mcr-1 and mcr-2. The PCR uses a single set of nondegenerative primers, and mcr variants can be differentiated by melt-curve analysis. Overnight culture enrichment was effective for amplifying colistin-resistant E. coli, even when initially present in numbers as low as 10 bacteria per gram of sample. The mcr-1 and mcr-2 genes were not found in any of the Ontario swine and poultry samples investigated.

Methicillin-resistant Staphylococcus aureus (MRSA) and Clostridium difficile are important human pathogens that are also carried by animals. The role of wild mammals on farms in their maintenance and transmission, however, is poorly understood. To determine if Norway rats (Rattus norvegicus) are potential carriers of these bacteria on Canadian farms, we tested 21 rats from swine farms in Ontario. The MRSA spa type t034 was isolated from 1 (4.8%) rat. This livestock-associated strain often colonizes pigs and pig farmers, suggesting that transmission among rats and pigs or environmental transmission is possible on pig farms. Clostridium difficile ribotype 078 was isolated from 1 rat from a different farm. This strain is associated with infection in piglets, calves, and humans. The identification of MRSA and C. difficile in Norway rats on farms in Canada adds to the growing knowledge about the role of rats in the ecology of these pathogens. Further studies are required to determine if rats play a part in the epidemiology of these pathogens on farms.