Campylobacter dynamics in conventiónal and antimicrobial-free (abf) swine and their environment

Campylobacter is an internationally recognized food-borne pathogen of public health importance. Food animals are important reservoirs of Campylobacter species, of which swine are known to be a main reservoir of Campylobacter coli. Conventionally reared swine receive antimicrobials in their feed at sub-therapeutic concentrations to enhance their growth; this use has been under debate due to associations with the development of antimicrobial resistant (AR) bacterial strains. However, AR bacteria are also shed by swine reared under no antimicrobial selection pressure, highlighting the potential role played by other factors including environmental reservoirs in the transmission of AR strains to pigs which needs to be identified. The objectives of this study were to 1) determine the Campylobacter prevalence and antimicrobial resistance profile in the ABF and conventional swine production systems at farm, slaughter, and the environment, 2) determine associations between potential risk factors and the prevalence of AR C. coli at the pre-harvest level, and 3) compare the population biology of antimicrobial resistant C. coli in the two systems. C. coli was the predominant species isolated at farm, slaughter, and environment in both production systems. The persistence of multidrug-resistant (MDR) C. coli in all the farm and slaughter stages in our study clearly indicates the ability of C. coli strains to disseminate across the production chain and persist in the farm and slaughter environment. Associations were determined between exposure to enrofloxacin, tetracycline, tiamulin, and resistance to ciprofloxacin and nalidixic acid, tetracycline, and macrolides, respectively in C. coli isolated from conventional pigs. The high frequency of MDR C. coli isolated from pigs reared in the ABF system, which did not receive antimicrobials for treatment or growth promotion, clearly indicate the lack of antimicrobial use does not necessarily result in absence of AR bacterial populations. Multiple MDR patterns were observed in the ABF ...