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U.S. Department of Health and Human Services

Animal & Veterinary

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FDA Veterinarian Newsletter January/February 2000 Volume XV, No I

FDA has made available three documents on antimicrobial resistance in food-producing animals. The first document is a draft "Risk Assessment on the Human Health Impact of Fluoroquinolone Resistant Campylobacter Associated with the Consumption of Chicken." To assist in evaluating the human health impact of antimicrobial use in animals, the Center contracted with a risk assessment expert to develop a risk assessment model. The risk assessment was intended to determine the feasibility of estimating risk to human health from resistant food borne pathogens associated with the use of antimicrobials in food-producing animals. Specifically, a mathematical model was derived to relate the prevalence of fluoroquinolone resistant Campylobacter infections in humans associated with the consumption of chicken to the prevalence of fluoroquinolone resistant Campylobacter in chickens.

The concern exists for several reasons. First, chickens carry foodborne pathogens, including Campylobacter and Salmonella. An estimated 20 percent of broiler chickens in the U.S. are contaminated with Salmonella, and more than 80 percent are contaminated with Campylobacter. Second, Campylobacter is the most common known cause of bacterial foodborne illness in the United States. Epidemiological investigations have found that chicken is the most common source of human infection. Third, Campylobacter apparently can develop resistance quickly when fluoroquinolones are used in both human and veterinary medicine. Fourth, fluoroquinolones are used in human medicine to treat gastrointestinal infections, such as campylobacteriosis and are important for use in many other therapeutic indications in human medicine. The risk assessment model could become a regulatory tool for assessing such risks in the future. This document is on CVM's Home Page.

The second document is a revision of the "Guidance for Industry: Consideration of the Human Health Impact of the Microbial Effects of Antimicrobial New Animal Drugs Intended for Use in Food-Producing Animals" (CVM guidance document 78.) This guidance document now states that FDA believes it is necessary to consider the potential human health impact of the microbial effects associated with all uses of all classes of antimicrobial new animal drugs intended for use in food-producing animals. To assess this impact, it may be necessary to evaluate two separate, but related aspects (1) the rate and extent of development of antimicrobial drug resistant enteric bacteria formed in the animal's intestinal tract following exposure to the antimicrobial new animal drug (resistance), and (2) changes in the number of enteric bacteria in the animal's intestinal tract that cause human illness (pathogen load.) Copies of the revised guidance document may be obtained from CVM's Home Page.

The third document is "FDA Response to Comments on A Proposed Framework for Evaluating and Assuring the Human Safety of the Microbial Effects of Antimicrobial New Animal Drugs Intended for Use in Food-Producing Animals." FDA had published a notice of availability of "A Proposed Framework for Evaluating and Assuring the Human Safety of the Microbial Effects of Antimicrobial New Animal Drugs Intended for Use in Food-Producing Animals," also known as the Framework Document, in the January 6, 1999, Federal Register. FDA made the Framework Document available to the public to initiate discussions with the scientific community and other interested parties on the agency's thinking about appropriate underlying concepts to be used to develop microbial safety policies protective of the public health. On January 25 and 26, 1999, the FDA held a meeting of the Veterinary Medicine Advisory Committee (VMAC) on the Framework Document to allow members to publicly consider answers to specific questions.

FDA stated that it would review the transcript of the VMAC meeting and any comments on the Framework Document that were submitted to FDA Dockets Management Branch (Dockets) and publish an analysis. This document is the Agency analysis of the transcript from the VMAC meeting and more than 50 comments to the Docket on Guidance Document #78 and the Framework Document. Copies of this analysis are on CVM's Home Page .

Readers interested in these documents who do not have access to the internet may receive single copies of these documents by calling or writing the FDA Veterinarian.