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The main objective is to minimize beef contamination with the human foodborne pathogens Shiga-like toxin producing Escherichia coli (SLTEC) including O157:H7 at the farm level. This will be accomplished by achieving three specific objectives. <P> The first objective is to identify beneficial dietary management practices that reduce the prevalence of SLTEC in beef cattle. <P> The second objective is to identify the role of diet in ruminal survival and proliferation of E. coli O157:H7 as a SLTEC model. <P> The third objective is to determine the efficacy of the best dietary treatments in minimizing survival and proliferation of E. coli O157:H7 in cattle.
NON-TECHNICAL SUMMARY: The negative effects and outbreaks of fodborne pathogens such as toxin-producing E. coli are on the rise. Beef cattle are known reservoirs of such pathogens. Post-harvest control methods alone have not been successful in reducing the risk of beef contamination of toxin-producing E. coli. Therefore, the role of pre-harvest control methods (e.g., dietary manipulation)is becoming important. This project identifies the dietray factors that can be implemented in beef cattle production systems to reduce the shedding of the toxin-producing E. coli. This on-farm management step is critically important to produce safer beef for humans.
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APPROACH: The first objective will be achieved by identifying beneficial dietary management practices that reduce the prevalence of SLTEC in beef (feedlot and pasture) and cull dairy cattle. This is a bi-state (California and Nevada) longitudinal epidemiological survey (2 years) of the effects of dietary management on prevalence and fecal shedding of SLTEC in beef and cull dairy cattle.The second objective will be achieved by identifying the role of diet in ruminal survival and proliferation of E. coli O157:H7 (as a SLTEC model) in vitro using the dual-flow continuous culture fermenter system (an artificial rumen model). This is based on the hypothesis that survival and proliferation of SLTEC in the rumen is a function of pH. Therefore, several pH treatments will be created by feeding diets containing different forage:concentrate ratios. The third objective will be achieved by determining the efficacy of the best dietary treatments (from the in vitro research) in minimizing survival and proliferation of E. coli O157:H7 in vivo using beef steers cannulated in the rumen, duodenum, and ileum. This allows monitoring survival and proliferation of the pathogen in various gastrointestinal tract segments.The research results will be integrated into education and extension programs targeting production of safer beef and continuous education of beef producers and students on food safety.
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PROGRESS: 2001/09 TO 2006/09<BR>
Assessment of prevalence of Shiga toxin-producing E. coli (STEC) in California over a one-year period with fecal sampling occurring once in each season involved cattle under different production systems and under various environmental conditions. This involved four large-scale dairy operations, four large-scale feedlots, four cow-calf operations on irrigated pastures, and six cow-calf operations on the range. The analysis of over 5,000 fecal samples illustrated the prevalence of STEC at rates ranging from 1.9 to 4.3% in feedlot cattle, from 1.9 to 5.0% in cattle grazing irrigated pastures, and from 0.7 to 18.6 in those grazing rangeland forages. Of the 34 STEC serotypes detected in beef cattle, 10 (i.e., E. coli O1:H2, O26:HUT, O125:H−, O128:H2, O146:H21, OUT:H2, OUT:H16, OUT:H19, OUT:H−, and OUT:HUT) are known to cause human illnesses and 22 (i.e., E. coli O1:H2, O86:H2, O86:H19, O125:H2, O125:H16, O125:H19, O125:H27, O125:H28, O125:HUT, O127:H2, O127:H19, O127:H28, O128:H16, O128:H20, O158:H28, O158:HUT, O165:HUT, O166:H2, O166:H6, O166:H20, O169:H19, and OUT:H20) have not been reported in cattle. Testing dairy cattle revealed prevalence rates ranging from 0.8 to 3.2%. Of the 9 serotypes detected, 3 (i.e., E. coli O15:H-, OUT:H-, and OUT:HUT) are known to cause human illnesses and 5 (i.e., E. coli O125:H20, O127:H19, O128:H20, O166:H6, and OUT:H20) have not been reported in cattle. Interestingly, E. coli O157 isolates (commonly associated with human illnesses in the US) were not found in the cattle tested. Because all our isolates produced at least one virulence factors (i.e., Shiga toxin 1, Shiga toxin 2, á-hemolysin, EHEC-hemolysin, and intimin), their health risk should not be ignored. The project resulted in two graduate students obtaining their M.S. degree in Animal Science and a student currently in the process of completing her Ph.D. in Cell and Molecular Biology. The investigators are cureently summarizing the data on pre-harvest control measures to decrease carriage and fecal shedding of STEC. The results along with the recommendations are expected to be published in 2007.
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IMPACT: 2001/09 TO 2006/09<BR>
The results from this project provide for the first time a database on prevalence of STEC in general in western US (California and Nevada). The database included identification of pathogenic strains of STEC and their potential impact on human health. Additionally, the project provided data on pre-harvest control measures with the highest potential to be implemented on the farm/ranch to decrease potential contamination of beef with these foodborne pathogens.