FDA counters study minimizing risk of antimicrobial resistance transference

Washington, D.C. -A peer-reviewed article raising concern that the banning of antibiotics in food animals may harm both human and animal health, is drawing criticism from the Food and Drug Administration (FDA).

The report, published in January's Journal of Antimicrobial Chemotherapy, based in London, says there is little scientific evidence that animal antibiotic use has a deleterious effect on human health. The multi-disciplinary panel made the conclusions after a review of more than 250 scientific studies on the subject.

FDA takes issue with the conclusions raised.

Dr. Linda Tollefson, deputy director for CVM, says "FDA has several concerns with the article; we are planning on writing a " 'letter to the editor' to address our major concerns. Because of our concerns, which generally cover the objectivity of the article as well as it accuracy, the article will have no impact on our current approach to antimicrobial resistance."

Dr. Linda Tollefson

Dr. Ian Phillips, MD, principal author and emeritus professor of medical microbiology at the medical school of Guy's and St. Thomas' Hospitals, University of London, says in a prepared statement, "The scientific evidence shows that the actual risk of transfer of antibiotic resistant organisms from animals to humans caused by the use of antibiotics in food animals is extremely small and in some cases zero."

Phillips adds, "The European Union applied the 'precautionary principle' and set aside scientific evidence, and so made decisions about antibiotics that have, in fact, damaged animal health and not provided any benefits to human health. We need to advance science and risk assessments to help make sound, evidence-based and balanced decisions in the United States and around the world."

The report was created by an independent advisory board to the Animal Health Institute (AHI), and includes Phillips, Ron N. Jones, MD, principal investigator of Sentry Antimicrobial Resistance Surveillance program; Mark Casewell, BSc, M.D., FRCP, FRCPath, University of London; Cox; Brad De Groot, M.S., DVM, Ph.D., Kansas State University, Manhattan, KS, and Livestock Information Services, Callaway, NE; Christian Friis, DVM, Ph.D., Royal Veterinary and Agricultural University, Copenhagen, Denmark; Charles Nightingale, MS, Ph.D., Hartford Hospital, University of Connecticut, Hartford, CT; Rodney Preston, Ph.D., Texas Tech University, Lubbock, TX; and John Waddell, DVM, MBA, Sutton Veterinary Clinic, Sutton, Neb. The association represents animal health manufacturers.

Ron N. Jones, MD

Tollefson argues, "There is a great deal of evidence demonstrating an association between antimicrobial use in animals and antimicrobial resistance in humans. The majority of evidence is found in Salmonella and Campylobacter, but instead the authors elect to concentrate on Enterococcus organisms. More importantly, there is accumulating evidence that antimicrobial resistance among bacteria isolated from humans resulting from the use of antimicrobial agents in food animals results in human health consequences."

It is an issue

The panel of experts reviewed more than 250 studies and available data in an attempt to determine whether or not there is a risk to public health by animal agriculture using antibiotics. The conclusions, Waddell adds, are that "the possibility exists that there could be transfer of resistance from animal use to humans, but the probability is very unlikely."

Waddell explains that the literature review also gave the panel a chance to assess the antibiotic resistance trends in Europe following the ban on growth promotants (low-levels of antibiotics used in feed to promote growth). The report suggests that surveillance data from Europe and the United States shows numerous disconnects in the patterns of resistant bacteria in animals and humans, making it unlikely that there is or has been widespread transference of resistant bacteria via the food supply, the panel concludes. Jones explains that since the ban, the number of cases of food-borne illness has increased as well as the resistance that they have found on human isolates. "It helped put credence to our conclusions that there isn't a link and if there is, it is not significant."

Trends in Europe

The report also says that the European ban on antibiotics to promote growth has not reduced antibiotic resistance levels in humans in Europe, U.S. data shows the incident of antibiotic resistant foodborne pathogens is generally declining as has the number of cases caused by food-borne bacteria.

"After examining the extensive surveillance data available, no significant benefits to human health as a result of European ban are evident, while it is clear that resistance in foodborne pathogens has decreased in the U.S.," Jones says.

Tollefson says that "Several studies demonstrating these effects will be published in 2004, but recent review articles on the human health consequences that have resulted from the use of antimicrobial agents in food animals is available." (Bazra and Travers, 2002; Travers and Bazra, 2002)

Tollefson adds, "Moreover, an expert consultation in December 2003 convened by FAO, International Office of Epizootics and the World Health Organization concluded 'there is clear evidence of adverse human health consequences due to resistant organisms resulting from on-human usage of antimicrobials.' "

Tony Cox, co-author and president of Cox Associates, an applied research company specializing in health risk analysis and operations research modeling, adds, "We agree with the World Health Organization and the International Office of Epizootics that sound policy decisions must be based on scientific risk assessments that address the likely future human health consequences of proposed risk management actions."

Waddell adds, "Continued use of antibiotics in food animals is important to animal health and welfare, and food safety. We will continue to follow the principles of prudent use and rely on surveillance and risk assessment to ensure safe use of antibiotics to keep animals healthy."