A new study by scientists from the US Department of Agriculture (USDA) has found similar levels of antimicrobial resistance (AMR) in pork chops from pigs raised without antibiotics and those raised conventionally.
For the study, published yesterday in the Journal of Food Protection, USDA researchers cultured bacteria from 372 pork chop samples from three food service suppliers that obtained their products from multiple harvesting facilities. Of the 372 samples, 190 came from conventional production systems and 180 came from "raised without antibiotics" (RWA) production systems. They focused on AMR in Escherichia coli, Salmonella enterica, Enterococcus spp, and Staphylococcus aureus. In addition, they evaluated DNA from the samples for the presence of 10 AMR genes.
The results of the analysis showed that levels of eight types of resistant bacteria in the conventional and RWA samples—tetracycline-resistant E coli, Salmonella, and Enterococcus; third-generation cephalosporin-resistant E coli and Salmonella; nalidixic acid-resistant Salmonella; erythromycin-resistant Enterococcus; and methicillin-resistant S aureus—were similar regardless of the antibiotic use claims. The prevalence of AMR genes were also similar. Overall, the populations of AMR bacteria in the samples were a small fraction of the aerobic bacterial population.
The authors of the study, who noted similar findings in conventionally raised and RWA ground beef last year, say that because the samples came from only three suppliers, they can't extrapolate the findings to the entire US retail pork supply. They also note that the findings do not conflict with reports that antibiotic use during swine production increases the presence of AMR bacteria in pig feces.
They conclude, however, that the study provides new evidence that antibiotic use in US swine production does not significantly increase the presence of AMR bacteria in pork products.