Purpose: What are the antibiotic resistance profiles of bacteria in agricultural production environments when antibiotics are not used for production purposes? All-natural, pasture-raised production systems where antibiotics are not used nor have been used historically should allow us to better determine background levels of antibiotic resistance in relevant bacteria associated with broiler chicken production.
Methods: Fifteen all-natural, pasture-raised broiler flocks were sampled along the entire “farm-to-fork” continuum, including fecal and soil samples during grow-out, cecal content and carcass rinses during processing, and carcass rinses of the final products delivered to the consumer. Traditional culture methods were used to isolate 3 zoonotic bacterial pathogens (Salmonella, Campylobacter, and Listeria) and generic Escherichia coli and their resistance profiles were determined using the CDC’s NARMS protocol.
Results: Sensitivities to a variety of antibiotics were found for not only generic E. coli isolates, but also for the three zoonotic bacterial pathogens, from various points along the “farm-to-fork” continuum. AST profiles did not appear to be dependent on species/serotype of each pathogen, nor where along the “farm-to-fork” continuum the pathogen was isolated.
Significance: While not surprising, these results show that background levels for resistance in these production systems need to be considered when determining the causal effect of antibiotic use within the production animals to the proliferation of antibiotic resistance organisms.