New research examining link between antibiotic use in farm animals and antibiotic resistance in humans leads to more questions
As controversy continues concerning the use of antibiotics in food animals and the relationship to drug-resistant infections in humans, a team of interdisciplinary scientists at the Medical University of South Carolina and the Charleston VA Medical Center Research Service reviewed published literature for evidence of a relationship between antibiotic use in agricultural animals and drug-resistant foodborne Campylobacter infections in humans, commonly known as campylobacteriosis.
According to the 2013 CDC Antibiotic Resistance Threats Report, two of the eighteen pathogens that are of concern in the United States may have a direct link to agriculture – one of them being Campylobacter.
Campylobacter can cause foodborne illness when food is not properly handled and cooked, regardless of whether it carries any specific antibiotic resistance. It is of concern because some people infected with Campylobacter develop severe arthritis; while others may develop Guillain-Barré Syndrome (GBS), which is one of the leading causes of acute paralysis in the U.S.
The study – conducted by veterinary and nutrition scientists and an infectious disease physician – reviewed 195 articles in the U.S., Canada and Denmark over the past five years and has been published in [volume 56, issue 13] of Critical Reviews in Food Science and Nutrition. Animals included in the reviewed studies were chicken, turkeys, pigs, beef cattle, and dairy cows.
The overall prevalence of Campylobacter and drug resistance found in the systematic review aligns with recent National Antimicrobial Resistance Monitoring System (NARMS) reports.
The research team found no conclusive evidence of a definitive link between use of antibiotics in food animals and emergence of drug-resistant Campylobacter. However, their findings did lead the team to important concerns about Campylobacter.
For example, recent cases of Campylobacter infections have been linked directly to drinking raw milk or eating food products made from raw milk. It is important to note the USDA and FDA do not recommend consuming raw cow's milk.
Lead scientist M.A. McCrackin, D.V.M., Ph.D. remarked, "There is still much more research to be done. The agriculture and health care industries, along with the scientific community and government regulatory agencies, must work collaboratively with the human health community in order to ensure safe, humane, and affordable food sources to the public."
Richard A. Carnevale, V.M.D., Vice President for Regulatory, Scientific and International Affairs at the Animal Health Institute (AHI), who funded the study, refers to the medical and veterinary collaborative approach as an "integrated, 'one-health' approach."
"The agriculture community recognizes that there is more that can be done to protect the effectiveness of antibiotics, which is the goal of both the animal and human health communities. By the end of the year, the agriculture community will be in full compliance with the FDA mandates — Guidances 209 and 213 — which eliminate the use of medically important antibiotics for growth promotion purposes and requires veterinary approval for all remaining uses in feed through the veterinary feed directive," said Dr. Carnevale.
Principal investigator on the study, Bernadette Marriott, Ph.D., stated, "Our research results underscore the need for both veterinarians and physicians to work together as we advance toward solutions to concerns about antibiotic resistance."
About the study authors
MUSC authors of this study are: M.A. McCrackin, D.V.M., Ph.D., Kristi Helke, D.V.M., Ph.D., Ashley Galloway, M.S., R.D., Ann Z. Poole, M.Ed., Cassandra Salgado, M.D., M.S., and Bernadette P. Marriott, Ph.D. Dr. McCrackin is also employed by the Ralph H. Johnson VAMC. A similar systematic review of Salmonella was also conducted and the findings are expected to be published next year.
The authors state that they are solely responsible for the contents of the study, its results and conclusions. The contents of this article and the contents of the authors' study represent the views and findings of the authors and do not represent the views of the Department of Veterans Affairs, the United States Government, or MUSC.
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