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U.S. Department of Health and Human Services

Animal & Veterinary

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FDA Veterinarian Newsletter May/June 1999 Volume XIV, No III

In FY 98, FDA funded seven (7) cooperative agreements under the President’s Food Safety Initiative. The primary objective of these projects is to study the microbiological hazards associated with the food animal production environment which includes animal feeds. FDA/CVM has appointed project officers to monitor and work with principal investigators in conducting the research studies, which are described below.

Dr. Dale Hancock is the principal investigator for a project at Washington State University titled "On-farm Risk Factors for Zoonotic Enteropathogens Associated with Cattle Feed and Water." The goal of this study is to reduce the prevalence of cattle infected on-farm with those zoonotic bacterial enteropathogens that are important causes of human foodborne infections. This approach complements efforts to ameliorate the contamination of bovine-origin foods through improved slaughter, processing, and retail procedures and, in turn, to reduce the risk of cross-contamination of other foods during preparation. Reduction of bovine infections with these agents will also reduce environmental contamination and will decrease their transmission to humans by direct contact and by vehicles other than foods of bovine origin. The project will focus on two specific agents: Escherichia coli serotype 0157:H7(0157) and Salmonella enterica serotype Typhimurium phage type DT104 R-type ACSSuT. For the purposes of this study, all Salmonella enterica serovars (SAL) will be included and the on-farm aspect will be limited to dairy farms only.

Dr. Charles Kaspar, University of Wisconsin, is directing a project titled "Waterborne Dissemination of Escherichia coli 0157:H7." Despite advances in detection methodologies and our understanding of virulence, comparatively little is known about the dissemination of E. coli 0157:H7 between farms and cattle. Each year E.coli 0157:H7 is estimated to cause between 7,000 to 20,000 cases, with 150 to 300 deaths. Therefore, an understanding of the dissemination and persistence of E. coli 0157:H7 among cattle is particularly important since ground beef is the primary food associated with outbreaks involving this human pathogen. The long-term goals of this study are to further define the farm ecology of E. coli 0157:H7 in order to understand and ultimately control the dissemination of this important foodborne pathogen in cattle. Dr. Kaspar hopes this project will provide valuable information on waterborne transmission in cattle of this important human pathogen and provide a potential point for on-farm control.

Dr. David Acheson, New England Medical Center, Boston, MA, is the principal investigator for the study titled "STEC, Salmonella Virulence and Antibiotic Resistance in Cattle and Feed." Since new varieties of foodborne illnesses emerge almost daily, it has never been more important to ensure the microbiological safety of our food supply. The focus of this work is on two groups of important foodborne pathogens: Shiga toxin producing E. coli (STEC), e.g., E. coli 0157:H7, and Salmonella. They will collaborate with investigators at Kansas State University who will provide samples and isolates. They will isolate and characterize STEC of multiple serotypes from cattle and animal feed for known human virulence factors (Shiga toxin 1 or 2 expression, hemolysin, attachment to epithelial cells, etc.) In addition, they will investigate the fate and transmission dynamics of antibiotic resistance in human foodborne pathogens. The long-term goal of this study is to establish baseline data on the longitudinal epidemiology and clonality of two important foodborne pathogens, STEC and Salmonella, and to provide a better idea of the prevalence of pathogenic STEC in cattle and feed, and how these move from feed to animals and change in animals with time.

Dr. James Russell, Agricultural Research Service, USDA, Ithaca, NY, is the principal investigator for a study titled "Factors Affecting Numbers of Acid-Resistance Escherichia coli in Cattle." Preliminary findings indicate that grain feeding, a practice common in the American cattle industry, seems to increase the numbers of E. coli as well as its acid-resistance. Most U.S. beef cattle are also fed the ionophore, monensin, and preliminary experiments indicated that E. coli is very resistant to this antibiotic. The long-term objectives of this study are to define the role of grain-feeding and feed additives in the dissemination of acid-resistant Escherichia coli from cattle, and to find dietary strategies that could reduce the numbers of acid-resistance E. coli in cattle feces. Dr. Russell expects to define relatively simple dietary changes that could reduce carcass contamination and foodborne illness by the withdrawal of monensin and the feeding of forage rather than grain in the period just before slaughter.

Dr. Marcus Zervos, William Beaumont Hospital, Royal Oak, MI, is conducting a study titled "Survey of Antimicrobial Resistance Enterococci in Animals." One of the most formidable treatment problems that has emerged recently has been vancomycin-resistant Enterococus faecium (VREF). Data from the Michigan Department of Public Health Sentinel Surveillance Hospital System indicated resistance rates of 45 percent to vancomycin in E. faecium in the fourth quarter of 1997. Since little is known about reservoirs for resistant strains and risk factors outside of the hospital setting, the incidence of resistant enterococci in food animals and the role of these animals as a source of resistance strains or "new" resistance genes that can be acquired by humans is not defined. The overall purpose of this three-year project is to gain a better understanding of the prevalence and spread of antibiotic resistant enterococci in food animals which are essential in the design of control and prevention strategies for human acquisition.

Michael Doyle, University of Georgia, is monitoring a study titled "Control of EHEC in Cattle by Probiotic Bacteria." Shiga toxin-producing enterohemorrhagic E. coli (EHEC), including 0157:H7, 026:H11, and 0111:NM, are a group of important human pathogens causing hemorrhagic colitis and hemolytic uremic syndrome (HUS). Increased incidences of these outbreaks have occurred in the past decade. Cattle, especially young animals, have been implicated as a principal reservoir, with undercooked ground beef being the major vehicle of foodborne outbreaks. However, apple juice, lettuce, and water-associated outbreaks have increased recently. Methods to reduce or eliminate carriage of E. coli 0157:H7, 026:H11, and 0111:NM in cattle are needed to decrease the risk of transmitting these pathogens through food and the environment. The goal of this study is to reduce the carriage of EHEC in cattle by administration of three probiotic bacteria. Results from this research will provide a practical critical control point for cattle producers to use at the farm to reduce meat and environmental contamination (via manure) by EHEC, as well as insights into the colonization mechanisms of E. coli in the gastrointestinal tract of calves.

Ann Draughton, University of Tennessee, is the principal investigator for the study titled "Evaluation and Use of BAM/FDA and Rapid Methods for On-farm Survey." This project will evaluate performance of existing Bacteriological Analytical Manual (BAM) methods and rapid microbiological methods for their ability to detect/isolate Escherichia coli 0157:H7, Yersinia enterocolitica, Salmonella spp., and Campylobacter jejuni in farm environmental samples associated with dairy cattle, swine, and poultry. This will be done by inoculating feeds and other farm environmental samples with known populations of these four human pathogens and determining recovery using BAM methods and several commercially available microbiological tests. In addition, they will conduct surveys of dairy cattle, swine, and poultry production environments to establish baseline data relative to occurrence of the above pathogens. The survey will include multiple sites on the bodies of cows, pigs, and chickens, animal feeds, feces, bedding, and other environmental sites that could serve as reservoirs for these bacteria. Hopefully, this information will be helpful in developing management strategies to reduce colonization of farm animals with human foodborne pathogens.

All of the above research is now ongoing, and is expected to take up to three years to complete. Funding amounts range from $72,530 to $198,192 per study per year. For further information about any of these agreements, please contact Dr. David B. Batson, Center for Veterinary Medicine (HFV-502), Food and Drug Administration, 8401 Muirkirk Rd., Laurel, MD 20708, 301-827-8021.