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U.S. Department of Health and Human Services

Animal & Veterinary

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by Linda Tollefson, D.V.M., M.P.H., Marcia Headrick, D.V.M., M.P.H., Roger Jones, Ph.D., and Joseph Paige, D.V.M., M.P.H.
FDA Veterinarian Newsletter November/December 1998 Volume XIII, No VI

Several Center for Veterinary Medicine (CVM) officials attended the Emerging Antibiotic Resistance in Food Borne Enteric Pathogens: Epidemiology, Public Health Risks, and Control Strategies symposium in Athens, Georgia, August 31 - September 3. A wide variety of presentations on antibiotic resistance including animal health and industry perspectives provided impetus for animated discussion. The symposium was co-sponsored by the United States Department of Agriculture’s (USDA) Agricultural Research Service (ARS), the Food and Drug Administration’s (FDA) CVM, and the Center for Disease Control and Prevention (CDC).

Dr. Jane Robens, USDA ARS, opened the conference with an overview of the National Academy of Sciences (NAS) report on The Use of Drugs in Food Animals. Dr. Robens reported that the NAS report praised the interagency cooperation between FDA, CDC, and USDA in carrying out the activities of the National Antimicrobial Resistance Monitoring System.

The first session focused on the Animal Health Industry perspective and was moderated by Dr. Scott Wells, USDA ARS. Representatives from the pork, beef, dairy, and poultry industries described their efforts to provide a safe, wholesome food supply while minimizing the opportunity for antimicrobial resistance development. Efforts described by industry representatives to prevent antimicrobial resistance development in food animals included on-farm research, support of the prudent use of antibiotics, an established and mandated withdrawal period, use of competitive exclusion products, good management practices, and quality assurance programs. Dr. Jarrett, President of the Bovine Practitioners Association, described the United States food supply as the most wholesome and least expensive food supply in the world.

CVM’s Dr. Linda Tollefson chaired a session on Public Health Perspectives that included representatives from several national consumer organizations; Dr. Lieberman represented the Center for Science in the Public Interest, Dr. Mellon represented the Union of Concerned Scientists, and Dr. Goldberg represented the Environmental Defense Fund. Dr. Sharon Thompson also participated in this session and gave an excellent overview of CVM's approach to the antibiotic resistance issue and CVM’s plans to address it.

Data from the National Antimicrobial Resistance Monitoring System was highlighted as well as results from the Canadian, Danish and German systems. An entire day was devoted to excellent presentations on the epidemiology of various food borne pathogens and approaches for prevention and control.

Of particular interest was a presentation by USDA ARS scientist Dr. Norman Stern describing an ongoing National Poultry Epidemiology Study. The study is a collaborative effort between USDA ARS, USDA Food Safety Inspection Service (FSIS), and the broiler producers. The National Poultry Epidemiology Study includes the collection of a variety of microbiological samples from poultry and their environment in five representative regions of the U.S. The one-year study includes five of the 20 largest integrated poultry producers and samples two poultry houses per operation. Salmonella and Campylobacter isolates will be identified and collected from sample cultures. Antimicrobial sensitivity testing will be conducted on the Salmonella and Campylobacter isolates through the National Antimicrobial Resistance Monitoring System. A survey is also being conducted as part of the study that includes determination of antibiotic use practices in poultry. The study results will help determine on-farm antimicrobial resistance prevalence and possible risk factors for resistance development. USDA hopes to continue the study for an additional year, but funding is uncertain at this time.

A session entitled "Approaches for Prevention and Control" chaired by Dr. Stan Bailey, addressed Campylobacter, Salmonella, and E. coli 0157:H7 control during animal production. Several presentations on competitive exclusion (CE) culture (a.k.a. probiotics) methods for reducing two of the above pathogens were included in the session.

Dr. Mike Doyle discussed the use of bovine probiotic E. coli cultures to reduce or eliminate carriage of Shiga toxin-producing enterohemorrhagic E. coli (EHEC), including 0157:H7, 026:H11, and 0111:NM in cattle. Dr. Doyle’s research demonstrates that many of these probiotic cultures show potential both as prophylactic and therapeutic agents in calves.

Dr. Stan Bailey presented evidence from his research in competitive exclusion culture use in poultry. Dr. Bailey’s work demonstrates that mixed microbial cultures derived from pathogen-free chickens can effectively colonize newly hatched chicks; thus preventing colonization from ubiquitous Salmonella.

Dr. Robin Anderson provided information on the use of CE cultures primarily in swine in a talk entitled "Competitive Exclusion: Potential for and Environmentally Compatible Pathogen Control Strategy." CE culture intervention strategies look very promising for reducing Salmonella shedding in swine.