We know that salmonella is one of the most important food-borne pathogens in the United States, and that some salmonella populations have developed resistance to one or more antibiotics. Research also has found antibiotic resistance in salmonella derived from animals at the farm level. However, studies linking food-borne illness and drug-resistant pathogens at the retail level with practices back on the farm are lacking, according to a new research review sponsored by the Animal Health Institute.

Researchers at the Medical University of South Carolina (MUSC) and the Charleston VA Medical Center Research Service conducted the review, and their summary, titled “Effects of antimicrobial use in agricultural animals on drug-resistant foodborne salmonellosis in humans: A systematic literature review,” is published in the journal Critical Reviews in Food Science and Nutrition.

The researchers reviewed 104 articles in the United States, Canada, Denmark, Scotland and Ireland over the past five year, including studies on chickens, turkeys, pigs, beef cattle and dairy cows.

The authors say their findings on the overall prevalence of Salmonella and drug-resistance align with recent National Antimicrobial Resistance Monitoring System (NARMS) report, showing that 81% of Salmonella from human infections carried no resistance to any antibiotic, while Salmonella resistance rates in animals vary by the antibiotic tested.

The review found six published articles showing an increase in drug-resistant bacteria associated with animals from conventional production systems versus those from antibiotic-free operations. They did not, however, find any studies that followed those animal-associated drug-resistant bacteria from farm to retail.

Lead scientist Kristi Helke, DVM., PhD, says "While there were some studies worth noting in our review, it is most apparent that there is a greater need for a more robust data collection system and heightened publication expectations in the U.S. for transparency in antibiotic usage in both animals and humans. There is still much more research to be done. The agriculture and healthcare industries must work hand-in-hand with the scientific community, government regulatory agencies and human health community in order to ensure safe, humane, and affordable food sources to the public."