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The global food animal industry faces a growing concern regarding antimicrobial resistance (AMR), primarily driven by the use of antimicrobials (AM) for the treatment, control, and prevention of diseases. Addressing this challenge requires promoting responsible antimicrobial use (AMU) practices. In 2019, the province of Québec, Canada, took a significant step by implementing a regulation that limits the use of AM of very high importance for human medicine (category I AM as defined by Health Canada) in the food animal industry. However, the implementation of such regulation can significantly influence behavioral shifts among producers, contributing to the wider effort against AMR. Therefore, the objective of this observational study was to describe the perceived changes in dairy producers' knowledge and on-farm practices following the implementation of this regulation, using a cohort design. Data collection involved administering questionnaires to 87 dairy producers from 3 regions of the province of Québec (Estrie, Montérégie, Centre-Du-Québec) before (2017-2018) and after (2020-2021) the implementation of the regulation. The questionnaires explored the descriptive characteristics of farms, the knowledge of producers about the categorization of AM, the on-farm treatment practices, and the perceived effects of the regulation. Statistical analysis included t-tests and McNemar tests to compare the paired data obtained using the 2 questionnaires. The results indicated an increase in the knowledge score (the number of AM correctly categorized by the producers by their importance for human medicine) after the implementation of the regulation, suggesting an improved understanding of the categorization of AM based on their importance for human medicine. Trends in AMU practices for treating clinical mastitis and reproductive diseases suggested that category I AM were less likely to be reported as the primary treatment after the regulation, whereas category II AM were more often reported as primary treatment. Adoption of the selective dry cow therapy method significantly increased, whereas the use of teat sealants remained unchanged. Moreover, producers had divergent perceptions regarding the effect of the regulation on the cure rates and disease frequencies. This disparity emphasizes the need for comprehensive data collection to discern the risks associated with such regulatory shifts. The study acknowledges several limitations, including the potential for recall bias, confirmation bias, and desirability bias. Despite these limitations, this study shows that implementing regulations to encourage responsible AMU drives positive transformations in producers' knowledge and on-farm practices. This underscores the pivotal effect of proactive interventions in combating the escalating threat of AMR within the global food animal industry., (The Authors. Published by Elsevier Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).)

Objectives: This study investigated the prevalence of Escherichia coli (E. coli) colistin resistance and mcr-1 and mcr-2 genes among extended-spectrum β-lactamase (ESBL)/AmpC-producing E. coli isolates recovered from chicken feces in Canada (Quebec), Senegal and Vietnam, and evaluated the susceptibility pattern of the colistin-resistant E. coli isolates to other clinically relevant antimicrobials., Methods: A total of 327 potential ESBL/AmpC-producing E. coli isolates from chicken farms in Canada (Quebec), Senegal and Vietnam were analysed for colistin susceptibility by broth microdilution method and for the presence of mcr (1-2) genes by PCR. The pmrA and pmrB genes of colistin-resistant E. coli isolates, in the absence of mcr (1-2) genes, were sequenced. Antimicrobial resistance phenotypes of colistin-resistant E. coli isolates were determined by disk diffusion., Results: None of the 108 potential ESBL/AmpC-producing E. coli isolates from seven farms in Canada were colistin-resistant or possessed mcr-1 or mcr-2 gene. A low prevalence of 2.2% of colistin resistance was observed in 93 Senegalese isolates from the 15 sampled farms, although neither mcr-1 nor mcr-2 gene was found. A prevalence of 8.7% of colistin resistance was observed among 126 Vietnamese isolates from two of the four sampled farms. The mcr-1 gene was detected in 85% of the 13 phenotypically colistin-resistant isolates. Moreover, all colistin-resistant isolates presented a multidrug-resistant phenotype., Conclusions: The co-existence of the mcr-1 and ESBL/AmpC genes and the very high level of multiple drug resistance in all colistin-resistant E. coli isolates obtained from sampled chicken farms in Vietnam is a major concern., (Copyright © 2019 International Society for Antimicrobial Chemotherapy. Published by Elsevier Ltd. All rights reserved.)

Antimicrobial resistance (AMR) is a global health issue, particularly when it affects critically important antimicrobials such as third-generation cephalosporins (3GC). The objective of this study was to characterize Escherichia coli isolates from healthy chickens in Québec in farms where ceftiofur has been administered to chickens in ovo over a long period with regard to their AMR, multidrug resistance (MDR), potential virulence, clonality, and possession of plasmids of the incompatibility groups carrying extended-spectrum beta-lactamases (ESBLs)/AmpC genes. More than 62% of indicator isolates were MDR with resistance observed for each of the nine classes of antimicrobials tested by disk diffusion. 3GC resistance was encoded by the bla CMY-2 gene (26.7% in indicator isolates), whereas bla CTX-M was only detected in isolates selected after supplementation with ceftriaxone (3 bla CTX-M-1 isolates). Examination of bla CMY-2 -positive isolates by pulsed-field gel electrophoresis showed clustering of isolates originating from different floors of the livestock building within farms. The bla CMY-2 gene was carried on replicon plasmids FIB, I1, K/B, and B/O, whereas bla CTX-M-1 gene was located on I1 as demonstrated by transformation experiments; some of these plasmids cotransferred nonsusceptibility against tetracycline or sulfonamides. In addition, six isolates, of which three were AmpC-producers, were defined as potential human extraintestinal pathogenic E. coli . In summary, this study showed that ESBLs/AmpC-producing E. coli isolates from apparently healthy chickens in Québec, Canada predominantly possess bla CMY-2 rather than bla CTX-M maybe because of the in ovo use of ceftiofur to prevent omphalitis and may be spread through clones or plasmids, and that some of these isolates could be capable of infecting humans.

The aim of this study was to investigate the evolution with time of ceftiofur-resistant Escherichia coli clinical isolates from pigs in Québec, Canada, between 1997 and 2012 with respect to pathotypes, clones and antimicrobial resistance. Eighty-five ceftiofur-resistant E. coli isolates were obtained from the OIE (World Organisation for Animal Health) Reference Laboratory for Escherichia coli. The most prevalent pathovirotypes were enterotoxigenic E. coli (ETEC):F4 (40%), extraintestinal pathogenic E. coli (ExPEC) (16.5%) and Shiga toxin-producing E. coli (STEC):F18 (8.2%). Susceptibility testing to 15 antimicrobial agents revealed a high prevalence of resistance to 13 antimicrobials, with all isolates being multidrug-resistant. blaCMY-2 (96.5%) was the most frequently detected β-lactamase gene, followed by blaTEM (49.4%) and blaCTX-M (3.5%). Pulsed-field gel electrophoresis (PFGE) applied to 45 representative E. coli isolates revealed that resistance to ceftiofur is spread both horizontally and clonally. In addition, the emergence of extended-spectrum β-lactamase-producing E. coli isolates carrying blaCTX-M was observed in 2011 and 2012 in distinct clones. The most predominant plasmid incompatibility (Inc) groups were IncFIB, IncI1, IncA/C and IncFIC. Resistance to gentamicin, kanamycin and chloramphenicol as well as the frequency of blaTEM and IncA/C significantly decreased over the study period, whereas the frequency of IncI1 and multidrug resistance to seven antimicrobial categories significantly increased. These findings reveal that extended-spectrum cephalosporin-resistant porcine E. coli isolates in Québec belong to several different clones with diverse antimicrobial resistance patterns and plasmids. Furthermore, blaCMY-2 was the major β-lactamase gene in these isolates. From 2011, we report the emergence of blaCTX-M in distinct clones., (Copyright © 2016 Elsevier B.V. and International Society of Chemotherapy. All rights reserved.)