Progress 09/01/08 to 08/31/12
Outputs
OUTPUTS: Escherichia coli O157:H7, a food borne human pathogen, resides as part of the normal flora in the hind gut of cattle and is shed in the feces. Cattle feces are a major source of contamination. We conducted three studies to address the following questions: Is the association between feeding DG and fecal shedding of E. coli O157 affected by the form of DG and inclusion level Is there a relationship between feeding DG and E. coli O157 prevalence in the carcass at harvest Are interventions that have shown promise in reducing fecal shedding of E. coli O157 have impact in cattle fed DG We determined prevalence of E. coli O157 in cattle (n=864) fed diets supplemented with 20 or 40% dried (DDG) or wet distillers grains (WDG) and assess whether removing DG from diets before slaughter affected fecal shedding of E. coli O157. Treatments were no DG, 20% DDG or WDG, and 40% DDG or WDG, and each was replicated in 14 pens. In phase 1, fecal samples were collected from each pen for isolation of E. coli O157 and detection of high shedders. In phase 2, half of the pens with DG were transitioned to the no-DG diet and samples were collected weekly for 4 weeks. Form of DG had no significant effect on fecal E. coli O157 shedding. Prevalence of E. coli O157 and high shedders were not different between diets with 0 or 20% DG; however, cattle fed 40% DG had a higher prevalence and more high shedders than cattle fed 0 or 20% DG. In phase 2, there were no differences between DG form, inclusion level, or removing DG from diets. A cross-sectional study to evaluate the relationship between feeding DG and E. coli O157 presence and magnitude in cattle feces, and presence on hides and carcasses at harvest was done. Fecal, hide and pre-intervention carcass samples were collected from up to 32 cattle on each of 45 truckloads presented to a Midwest abattoir. Fecal, hide and carcass prevalence of E. coli O157:H7 within truckload were significantly correlated with each other. We found 38.5% of hides and 10.5% of carcasses positive for E. coli O157. All truckload-level predictors significantly affected the probability of an E. coli O157-positive carcass, including presence of a high shedder within the truckload, high (> 25%) within-truckload fecal prevalence, and high (> 50%) within-truckload hide prevalence; the only significant animal-level predictor was having a positive hide. We conducted a study to determine the efficacy of a siderophore receptor and porin (SRP) proteins-based vaccine (VAC) and a direct fed microbial (DFM; Bovamine) for controlling fecal shedding of E. coli O157 in cattle fed a diet with 25% WDG. Cattle were randomly allocated into 40 pens and randomly assigned to: control, VAC, DFM, or VAC+DFM. The DFM was fed (106 CFU/animal/day of Lactobacillus) throughout the study period (84-88 days) and cattle were vaccinated at enrollment and again three weeks later. Fecal samples (30/pen) were collected weekly for four consecutive weeks. There were no significant interactions among treatments and time of sampling. However, vaccinated pens had lower (P < 0.05) overall prevalence of E. coli O157 and lower prevalence of high shedders than unvaccinated pens. PARTICIPANTS: Nagaraja, T. G., Dave Renter, Megan Jacob, Mike Sanderson, Dan Thomson, and Kelly Lechtenberg, Charley Cull, and Zachary Paddock T. G. Nagaraja: Microbiologist; Principal investigator; involved in all planning and decision making processes, managing funds, and overseeing laboratory analysis and reporting of results. David Renter: Epidemiologist; Co-Principal investigator; Responsible for the study design, sample size determinations, and statistical analysis; Also involved in all planning and decision making processes and overseeing laboratory analysis and reporting of results. Megan Jacob: Ph. D student in Microbiology; Graduate student coordinating sample collection and processing in laboratory, recording of data, and analysis of results of studies 1 and 2. Mike Sanderson: Epidemiologist; Involved in the study design and statistical analysis Dan Thomson: Feedlot nutritionist; Involved in setting up field studies Dr. Kelly Lechtenberg, Director of Research, Midwest Veterinary Services, Oakland, Nebraska. Responsible for the field study conducted in Nebraska; coordinated the purchase, handling, feeding and management of cattle in the feedlot. Laboratory technicians: Xiaorong Shi and Neil Wallace Xiaorong Shi: Responsible for bacteriological procedures and molecular analyses (PCR and PFGE typing of isolates). Neil Wallace: Responsible for bacteriological procedures, ordering supplies, maintaining inventory and supervising undergraduate students. Graduate students Ph. D. students: Charley Cull, Zac Paddock Charley Cull: DVM/Ph. D dual degree student; coordinated sample collection and processing in laboratory, recording of data, and analysis of results of the third study. Zachary Paddock: Ph. D degree student; Graduate student coordinating sample collection and processing in laboratory, recording of data, and analysis of results of the third study. Undergraduate students: A number of undergraduate students work part time in the laboratory. The students are trained in laboratory safety and analytical skills. TARGET AUDIENCES: Scientists, Veterinarians, Food Safety Inspection Agency, Cattlemen, Packers, Students The results from this study will be useful for the beef cattle, corn, and distiller's grains industries, as well as academic and governmental entities researching E. coli O157:H7. Results were presented at Food Safety meetings of the National Cattlemen's Beef Association (2011 and 2012) and Oral or poster presentations were made in the Conference of Research Workers on Animal Diseases in Chicago 9 (2010 and 2011) and Joint Meetings of the American Society of Animal Science and American Dairy Science Association (2010 and 2011). PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
The food supply in the United States is one of the safest in the world; however, food-borne illnesses do occur and frequently are associated with foods derived from animal agriculture. Besides food, there are other modes of transmission such as direct contact with cattle, exposure to contaminated water, and consumption of contaminated vegetables and fruits. Despite rigorous surveillance of meat processors by the USDA Food Safety and Inspection Service, the number of confirmed human illnesses caused by Shiga toxin-producing E. coli (STEC), particularly O157, continues at unacceptable levels. Because distiller's grains are widely used as cattle feed, it is important to determine their impact on prevalence of E. coli O157:H7 in cattle and subsequent contamination of carcasses. The information is useful to the cattle industry and provides an opportunity to modify diets to reduce the prevalence and pathogen load in cattle presented for slaughter. The studies confirmed that feeding DG to cattle is associated with increased fecal shedding of E. coli O157 and an increased number of cattle shedding at high concentrations. The form of DG (wet or dry) had no impact on E. coli O157 prevalence; however, fecal shedding of was dependent on DG inclusion level. In the phase 2 of the study, the prevalence was low (3.3%), which did not allow effective evaluation whether removal of DG had any effect on fecal prevalence of E. coli O157. The results in the second study indicated important animal and truckload-level risk factors for carcass contamination with E. coli O157. Although truckload-level correlations among fecal (both high and low shedders), hide, and carcass prevalence were demonstrated, the use of multivariable models to simultaneously quantify effects of multiple factors affecting carcass contamination provided a unique assessment of these factors. Interestingly, all truckload level factors (at least one high shedder, and high fecal and hide E. coli O157 prevalence within the cohort) significantly contributed to carcass contamination, whereas only one animal-level factor (hide contamination) was associated with carcass contamination. These data point to truckload or cohort level mitigation strategies, particularly those reducing hide contamination, being most effective in reducing E. coli O157 contamination of beef carcasses. Based on the third study, Bovamine, a DFM, at low dose (106 colony-forming units per animal per day), had no effect on fecal shedding or high shedders of E. coli O157. However, results indicated that a two-dose regimen of the SRP vaccine reduced fecal prevalence (efficacy of 53.0%) and prevalence of high shedders (efficacy of 77.3%) in feedlot cattle reared in the summer on a finishing diet with 25% distiller's grains. Therefore, the SRP vaccine may be an effective intervention for E. coli O157 control in potentially high risk populations of feedlot cattle. The combination of DFM and VAC was no more efficacious than VAC alone. The study was also used to assess the impact of SRP vaccine and Bovamine on another STEC, O26. Preliminary results suggested that the treatments had no significant effect on O26 shedding.
Publications
- Cull, C. A., Z. D. Paddock, T. G. Nagaraja, N. M. Bello, A. H. Babcock, and D. G. Renter. 2012. Efficacy of a vaccine and a direct-fed microbial against fecal shedding of Escherichia coli O157:H7 in a randomized pen-level field trial of commercial feedlot cattle. Vaccine (Accepted for Publication. Eprint available ahead of publication) Jacob, M. E., J. T. Fox, and T. G. Nagaraja. 2012. Prevalence of food-borne pathogens in organic beef. p 287-300. In: Organic Meat Production and Processing. S. C. Ricke, E. J. Van Loo, M. G. Johnson, and C. A. OBryan (eds.) Wiley-Blackwell, Ames, IA.
- Jacob, M. E. and T. G. Nagaraja. 2012. Use of direct-fed microbials as a preharvest food safety intervention in cattle. p 189-202. In: Direct-Fed Microbials and Probiotics for Animals: Science and Mechanisms of Action. T. R. Callaway and S. C. Ricke (eds.) Springer Publ., NY.
- Cull, C. A., D. G. Renter, Z. Paddock, N. M. Bello, A. H. Babcock, and T. G. Nagaraja. 2011. Effects of a vaccine and a direct-fed microbial on fecal shedding of Escherichia coli O157:H7 in pens of commercial feedlot cattle fed a diet supplemented with distillers grains (Abstract # 087). Paper presented in the Conference for Research Workers in Animal Diseases, Chicago, IL (Dec 4-6, 2011).
- Paddock, Z, D. G. Renter, C. A. Cull, L. A. Schaffer, X. Shi, J. Bai, and T. G. Nagaraja. 2011. Fecal shedding of Escherichia coli O26 in feedlot cattle from a field trial evaluating Escherichia coliO157:H7 vaccine and a direct-fed microbial (Abstract # 087). Paper presented in the Conference for Research Workers in Animal Diseases, Chicago, IL (Dec 4-6, 2011).
- Schaefer, L., Z. Paddock, C. Cull, X. Shi, S. Li, J. Bai, T. G. Nagaraja, and D. Renter. 2110. Prevalence of Shiga toxin-producing Escherichia coli serogroup O26 in feces of feedlot cattle. (Abstract # 038). Poster presented in the Conference for Research Workers in Animal Diseases, Chicago, IL (Dec 4-6, 2011).
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Progress 09/01/10 to 08/31/11
Outputs
OUTPUTS: Escherichia coli O157:H7, a food borne pathogen, is an important public health concern. Cattle are natural reservoirs of this organism and shed the bacteria in their feces, which then can serve as a major source of contamination of human food and water. The goals of our research program are to develop improved methods to detect and quantify E. coli O157:H7, improve our understanding of the ecology of E. coli O157:H7 in cattle operations, and to identify and test on-farm intervention strategies for control of E. coli O157:H7. A multiplex PCR procedure that detected six major virulence genes, fliC, stx1, stx2, eae, rfbE, and hlyA, in E. coli O157:H7 was developed. The procedure was validated with pure cultures of cattle and human strains. In fecal samples spiked with an E. coli O157 strain, the PCR reaction amplified all six genes if the concentration of E. coli O157 was 104 CFU/g of feces, but with an enrichment step the detection limit was 10 CFU/g of feces. We defined and compared pulsed-field gel electrophoresis (PFGE) profiles of E. coli O157 isolated from cattle feces and carcass samples to evaluate relationships between beef carcass contamination and fecal shedding of E. coli O157 at harvest. Among all isolates, there were 17 PFGE types (95% homology) and 37 subtypes (100% homology). Although E. coli O157:H7 is widely prevalent in cattle and cattle environments, the number of human cases remain relatively low, suggesting possible strain diversity and differences in virulence between human and bovine strains, but not producing Stx2 (toxin non-producing [TNP] strains) have been identified. In this study, 56 human clinical and 94 bovine strains were tested by PCR for stx2 upstream regions associated with toxin non-producing (TNP) strains and the Q933 gene. The percentages of human and bovine isolates positive for presence of the TNP regions were similar (57.1% and 53.1%, respectively), while a higher percentage of human isolates was positive for Q933 gene (89.3% vs. 54.3%). Stx2 production of ≥1:8 was found in 86.0% of human isolates compared to 26.3% of bovine isolates. Q933 was a better indicator of high Stx2 production by human and bovine isolates and may be a useful screening method to assess their potential to cause human disease. We evaluated the efficacy of an anti-Escherichia coli O157 siderophore receptor and porin proteins SRP-based vaccine in feedlot cattle naturally shedding the organism. Cattle were randomly allotted to 1 of 3 treatment groups: control, vaccinated with 2 ml per animal or 3 ml per animal with E. coli SRP vaccine subcutaneously 21 days apart. Control cattle were injected with sterile saline emulsified with an adjuvant. The SRP vaccine at the 3 ml dose reduced (P < 0.01) the prevalence of E. coli O157 compared to the control (17.7% vs. 33.7%). A similar numerical trend was observed with the 2 ml dose (29.1%), but differences were not statistically significant. Additionally, the 3 ml dose of SRP vaccine reduced the number of days cattle tested culture positive for E. coli O157, and the number of days cattle were identified as high-shedders compared to control. PARTICIPANTS: Nagaraja, T. G., Dave Renter, Jianfa Bai, Mike Sanderson, and Ludek Zurek T. G. Nagaraja: Microbiologist; Principal investigator; involved in all planning and decision making processes, managing funds, and overseeing laboratory analysis and reporting of results. David Renter: Epidemiologist; Co-Principal investigator; Responsible for the study design and statistical analysis; Also involved in all planning and decision making processes and overseeing laboratory analysis and reporting of results. Jianfa Bai: Molecular Biologist; Involved in PCR analyses of virulence genes Mike Sanderson: Epidemiologist; Involved in study design and statistical analysis Ludek Zurek: Medical Entomologist; Involved in studies on flies and E. coli O157:H7 Laboratory technicians: Xiaorong Shi and Neil Wallace Xiaorong Shi: Responsible for bacteriological procedures and molecular analyses (PCR and PFGE typing of isolates). Neil Wallace: Responsible for bacteriological procedures, ordering supplies, maintaining inventory and supervising undergraduate students. Graduate students Ph. D. students: Charles Dodd, Megan Jacob, Zac Paddock MPH students: Ethel Taylor M. S. Students: Callie Walker Graduate students are responsible for sample collection and processing in laboratory, recording of data, analysis of results, conference presentations and manuscript writing. Undergraduate students: A number of graduate students work part time in the laboratory. The students are trained in laboratory safety and analytical skills. TARGET AUDIENCES: Scientists, Veterinarians, Food Safety Inspection Agency, Cattlemen, Packers, Students PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
The food supply in the United States is one of the safest in the world; however, food-borne illnesses do occur and frequently are associated with foods derived from animal agriculture. Escherichia coli O157:H7 and other Shiga toxin-producing E. coli (non-O157 serotypes) are important food-borne pathogens that cause hemorrhagic colitis, hemolytic uremic syndrome and thrombocytopenic purpura in humans. Besides food, there are other modes of transmission such as direct contact with cattle (farm workers, farm visitors, children visiting fairs and petting zoos), exposure to contaminated drinking and recreational water, and consumption of contaminated vegetables and fruits. Despite rigorous surveillance of meat processors by the USDA Food Safety and Inspection Service following the 1994 regulatory declaration of E. coli O157:H7 as an adulterant in raw ground beef, the number of confirmed human illnesses caused by E. coli O157:H7 continues at unacceptable levels. Control strategies aimed at reducing the prevalence and concentration of E. coli O157:H7 in cattle feces, thus reducing the overall number of bacteria entering both the food and environmental pathways, may be the most effective approach for reducing the overall risk of human infections. Furthermore, effective control of E. coli O157:H7 in the beef food supply chain will require interventions at multiple levels and by multiple means. The goals of our research program are to develop improved methods to detect and quantify E. coli O157:H7, improve our understanding of the ecology of E. coli O157:H7 in cattle operations, and to identify and test on-farm intervention strategies for control of E. coli O157:H7. Previous published procedures to detect the six virulence genes required a minimum of two PCR reactions. The new procedure achieves amplification of all six genes in a single reaction. Our results indicate that cattle feces from both low- and high-shedders pose a potential risk for E. coli O157 contamination of carcasses. Truckload may be an important factor in the potential transmission of E. coli O157, but isolates from carcasses also may be similar to those from feces of cattle on different truckloads and harvest days. Human clinical strains of E. coli O157:H7 produce more Stx2 than strains isolated from cattle. The presence of Q933 gene is a better indicator of high Stx2 production and may be a useful marker to assess potential of cattle strains to cause human disease. The E. coli O157:H7 SRP vaccine may serve as a preharvest intervention to reduce the burden of E. coli O157:H7 on cattle presented for slaughter.
Publications
- Fox, J. T., J. S. Drouillard, and T. G. Nagaraja. 2009. Effects of mucin and its carbohydrate constituents on Escherichia coli O157 in batch culture fermentations with ruminal or fecal microbial inoculums. J. Anim. Sci., 87:1304-1313.
- Thornton, A. B., D. U. Thomson, J. T. Fox, G. H. Loneragan, D. T. Burkhardt, D. A. Emery, and T. G. Nagaraja. 2009. Siderophore receptor/porin proteins-based vaccination reduces prevalence and shedding of Escherichia coli O157:H7 in experimentally inoculated cattle. J. Food Prot. 72:866-869.
- Jacob M. E., J. T. Fox, J. S. Drouillard, D. G. Renter, and T. G. Nagaraja. 2009. Evaluation of feeding dried distillers grains with solubles and dry-rolled corn on the fecal prevalence of Escherichia coli O157:H7 and Salmonella spp. in cattle. Foodborne Path. Dis. 5:721-730.
- Thomson, D. U., G. H. Loneragan, A. B. Thornton, K. F. Lechtenberg, D. A. Emery, D. T. Burkhardt, and T. G. Nagaraja. 2009. .Use of a siderophore receptor and porin proteins-based vaccine to control the burden of Escherichia coli O157:H7 in feedlot cattle. Foodborne Path. Dis. 6:871-877.
- Fox, J. T., D. U. Thomson, J. S. Drouillard, A. B. Thornton, D. T. Burkhardt, D. A. Emery, and T. G. Nagaraja. 2009. .Efficacy of Escherichia coli O157:H7 siderophore receptor/porin proteins-based vaccine in feedlot cattle naturally shedding E. coli O157. Foodborne Path. Dis. 6:893-899.
- Walker, C. X. Shi, M. J. Sanderson, J. S. Sargeant, and T. G. Nagaraja 2010.. Prevalence of Escherichia coli O157:H7 in gut contents of beef cattle at slaughter. Foodborne Path. Dis. 7:249-255.
- Dodd, C., D. G. Renter, T. Fox, X. Shi, M. Sanderson, A. Nutsch, and T. G. Nagaraja. 2010. Genetic relatedness of Escherichia coli O157 isolates from cattle feces and pre-intervention beef carcasses. Foodborne Path. Dis. 7:357-365.
- Jacob M. E., D. G. Renter, and T. G. Nagaraja. 2010. Animal- and truckload-level associations between E. coli O157:H7 in feces and on hides at harvest and contamination of pre-evisceration beef carcasses. J. Food Prot. 73:1030-1037.
- Bai J., X. Shi and T. G. Nagaraja. 2010. A Multiplex PCR Procedure for detection of six major virulence genes in Escherichia coli O157:H7. J. Microbiol. Meth. 82:85-89.
- Jacob, M. E., K. F. Lechtenberg, L. L. Burnham, D. Haverkamp, and T. G. Nagaraja. 2110. Feeding MSE direct-fed microbials in finishing cattle decreases the fecal shedding of Escherichia coli O157:H7. Paper presented at the Midwest Animal Science and Dairy Science Associations Meeting, Des Moines, IA (Mar 15-17, 2010).
- Jacob, M. E., D. G. Renter, Z. D. Paddock, K. F. Lechtenberg, and T. G. Nagaraja. (2010). Feeding dried or wet distillers grains at varying inclusion levels to feedlot cattle affects the fecal prevalence of Escherichia coli O157:H7. Paper presented at the Midwest Animal Science and Dairy Science Associations Meeting, Des Moines, IA (Mar 15-17, 2010).
- Paddock, Z. D., C. E. Walker, J. S. Drouillard, D. G. Renter, and T. G. Nagaraja. Monensin level, supplemental urea, and administration of ractopamine on fecal shedding of Escherichia coli O157:H7 in feedlot cattle (Abstract # 1086). J. Anim. Sci 88 (E-Suppl.):854. 2010.
- Jacob, M. E., B. An, X. Shi, T. G. Nagaraja, and J. Bai. 2110. A multiplex, real-time PCR assay based on stx1, stx2, and rfbE for the quantification of Escherichia coli O157 in cattle feces (Abstract # 089). Paper presented in the Conference for Research Workers in Animal Diseases, Chicago, IL (Dec 7-9, 2010).
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Progress 09/01/09 to 08/31/10
Outputs
OUTPUTS: Escherichia coli O157:H7 is a food borne pathogen that causes gastroenteritis, ranging from mild to severe, in thousands of Americans each year. The organisms reside asymptomatically in the large intestine of cattle and are shed in the feces. Cattle feces are a major source of food and water contamination. Fecal shedding of E. coli O157:H7 in cattle is associated with many factors including season, geographic location, and diet. The use of cereal grains for ethanol production results in a co-product called distiller's grains (DG), which are used as cattle feed because of high energy and protein contents. Distiller's grains are a valuable feed commodity for cattle producers, and use of these co-products has increased with the expansion of the ethanol industry. We have reported that feeding distiller's grains are associated with an increased prevalence of E. coli O157:H7 in feedlot cattle. Distillers grains for use in cattle diets are available in wet (WDG) or dry (DDG) form. The association between feeding DG and E. coli O157:H7 prevalence has been shown with both forms of DG, but no study has directly compared the two forms. Also, level of DG supplementation in cattle diets generally ranges from 10 to 50% (dry matter basis) depending on whether the co-product is used as a protein or energy source. As a protein supplement, DG is included at 10 to 15%; as an energy source, the DG level is generally dictated by co-product availability and grain price. However, no study has specifically evaluated the relationship between E. coli O157:H7 prevalence and DG inclusion level. Evaluation of these two factors (form and inclusion level) is important for furthering our understanding of the association between DG and E. coli O157:H7 in cattle. We also were interested in determining whether removing the DG component of the diet would lower fecal prevalence of E. coli O157:H7. Such a strategy may lead to potential mitigation options and would provide further evidence of a positive association between feeding DG and E. coli O157:H7 prevalence in cattle. We conducted a two-phase study to (1) concurrently evaluate the effect of DG inclusion level and form on E. coli O157:H7 prevalence in feedlot cattle and (2) determine if removing DG from cattle diets subsequently reduces fecal prevalence of E. coli O157:H7. Eight hundred forty steers were allocated to 70 pens (12 steers/pen). Treatments were no DG (control), 20% DDG or WDG, and 40% DDG or WDG, and each was replicated in 14 pens. In phase 1, eight floor fecal samples were collected from each pen every 2 weeks for 12 weeks for isolation of E. coli O157:H7 and detection of high shedders. In phase 2, half of the pens with DG were transitioned to the no-DG control diet and pen floor fecal samples were collected weekly from all pens for 4 weeks. PARTICIPANTS: Megan Jacob, Nagaraja, T. G., Dave Renter, Mike Sanderson, Dan Thomson, and Kelly Lechtenberg, Megan Jacob: Ph. D student; Graduate student coordinating sample collection and processing in laboratory, recording of data, and analysis of results. T. G. Nagaraja: Microbiologist; Principal investigator; involved in all planning and decision making processes, managing funds, and overseeing laboratory analysis and reporting of results. David Renter: Epidemiologist; Co-Principal investigator; Responsible for the study design, sample size determinations, and statistical analysis; Also involved in all planning and decision making processes and overseeing laboratory analysis and reporting of results. Mike Sanderson: Epidemiologist; Involved in the study design and statistical analysis, Dan Thomson: Feedlot nutritionist; Involved in setting up field studies. Dr. Kelly Lechtenberg, Director of Research, Midwest Veterinary Services, Oakland, Nebraska. Responsible for the field study conducted in Nebraska; Coordinated the purchase, handling, feeding and management of cattle in the feedlot. Laboratory technicians: Xiaorong Shi and Neil Wallace, Xiaorong Shi: Responsible for bacteriological procedures and molecular analyses (PCR and PFGE typing of isolates). Neil Wallace: Responsible for bacteriological procedures, ordering supplies, maintaining inventory and supervising undergraduate students. Graduate students, Ph. D. students: Charles Dodd, Zac Paddock, Graduate students are responsible for sample collection and processing in laboratory, recording of data, analysis of results, conference presentations and manuscript writing. Undergraduate students: A number of undergraduate students work part time in the laboratory. The students are trained in laboratory safety and analytical skills. TARGET AUDIENCES: Scientists, Veterinarians, Food Safety Inspection Agency, Cattlemen, Packers, Students. The results from this study will be useful for the beef cattle, corn, and distiller's grains industries, as well as academic and governmental entities researching E. coli O157:H7. PROJECT MODIFICATIONS: No major modifications have been made to this project. The sample size was decreased to meet budget requirements. The number of pens was decreased from 84 to 70, and the number of cattle per pen was decreased from 15 to 12. The number of treatments was decreased from 7 to five (10% of wet and dried DG treatments were not used; however 20% and 40% of both wet and dried DG were maintained). It is not expected that these modifications will alter our ability to meet the objective, and sample size calculations were evaluated to ensure proper power would be retained to find treatment differences.
Impacts
A total of 3,350 fecal samples (six collections over 12 weeks) that included 670 from control cattle, 671 from the 20% DDG group, 666 from the 20% WDG group, 672 from the 40% DDG group, and 671 from the 40% WDG group were obtained. During phase 1, prevalence of E. coli O157:H7 was 20.8% and 3.2% for high shedders. Form of DG had no significant affect on fecal E. coli O157:H7 shedding. Prevalence of E. coli O157:H7 and high shedders were not different between diets with 0 or 20% DG; however, cattle fed 40% DG had a higher prevalence and more high shedders than cattle fed 0 or 20% DG (P ≤ 0.05). During phase 2, overall and high-shedder prevalence estimates were 3.3% and < 0.1%, respectively, and there were no differences between DG form, inclusion level, or removing DG from diets. The low prevalence of E. coli O157:H7 in cattle during phase 2 limited our ability to effectively evaluate whether removal of DG had any effect on fecal prevalence of E. coli O157:H7. These results confirm the previous observation that feeding cattle wet or dried DG can be associated with increased E. coli O157:H7 prevalence. This study also showed that not only overall prevalence but also high-shedder prevalence was dependent on DG inclusion level. Form of DG had no impact on E. coli O157:H7; however, fecal shedding was dependent on DG inclusion level. The food supply in the United States is one of the safest in the world; however, food-borne illnesses do occur and frequently are associated with foods derived from animal agriculture. Escherichia coli O157:H7 is an important food-borne pathogen that causes hemorrhagic colitis, hemolytic uremic syndrome and thrombocytopenic purpura in humans. Besides food, there are other modes of transmission such as direct contact with cattle (farm workers, farm visitors, children visiting fairs and petting zoos), exposure to contaminated drinking and recreational water, and consumption of contaminated vegetables and fruits. Despite rigorous surveillance of meat processors by the USDA Food Safety and Inspection Service following the 1994 regulatory declaration of E. coli O157:H7 as an adulterant in raw ground beef, the number of confirmed human illnesses caused by E. coli O157:H7 continues at unacceptable levels. Control strategies aimed at reducing the prevalence and concentration of E. coli O157:H7 in cattle feces, thus reducing the overall number of bacteria entering both the food and environmental pathways, may be the most effective approach for reducing the overall risk of human infections. Furthermore, effective control of E. coli O157:H7 in the beef food supply chain will require knowledge on the ecology of the organism in cattle and cattle operations. Diet is one of the major factors affecting prevalence of E. coli O157:H7. Because distiller's grains are widely used as cattle feed, it is important to determine their impact on prevalence of E. coli O157:H7 in cattle and subsequent contamination of carcasses. The information is useful to the cattle industry and provides an opportunity to modify diets to reduce the prevalence and pathogen load in cattle presented for slaughter.
Publications
- Jacob M. E., D. G. Renter, and T. G. Nagaraja. 2010. Animal and truckload level associations between E. coli O157:H7 in feces and on hides at harvest and contamination of pre-evisceration beef carcasses. J. Food Prot. 6:1030-1037.
- Jacob M. E., Z. D. Paddock, D. G. Renter, K. F. Lechtenberg, and T. G. Nagaraja. 2010. Inclusion of dried or wet distillers' grains at different levels in diets of feedlot cattle affects fecal shedding of Escherichia coli O157:H7. Appl. Environ. Microbiol. 76:7238-7242.
- Jacob, M. E., D. G. Renter, Z. D. Paddock, K. F. Lechtenberg, and T. G. Nagaraja. 2010. Feeding dried or wet distillers grains at varying inclusion levels to feedlot cattle affects the fecal prevalence of Escherichia coli O157:H7. Paper presented at the Midwest Animal Science and Dairy Science Associations Meeting, Des Moines, IA (Mar 15-17, 2010).
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Progress 09/01/08 to 08/31/09
Outputs
OUTPUTS: Escherichia coli O157:H7 is a foodborne pathogen capable of causing severe disease in humans. The bacteria reside asymptomatically in the gastrointestinal tract of cattle and are shed in the feces. Cattle feces are a major source of food and water contamination. The use of grains for ethanol production results in a co-product called distiller's grains (DG), which are used as cattle feed. We have reported that feeding ethanol co-products are associated with an increased prevalence of E. coli O157:H7 in feedlot cattle. However, no work has been done to see if the relationship between feeding DG and increased E. coli O157:H7 prevalence exists at harvest, the step where direct contamination of beef carcasses occurs. We conducted a cross-sectional study to evaluate the potential relationship between feeding cattle distiller's grains and E. coli O157:H7 presence and magnitude in cattle feces, and presence on hides and carcasses at harvest. Fecal, hide and pre-intervention carcass samples were collected from up to 32 cattle on each of 45 truckloads presented to an abattoir. Direct plating was used to identify cattle shedding high levels of E. coli O157:H7 in feces, and enrichment and selective culture were used to assess fecal, hide, and carcass prevalence. Feedlots were contacted by telephone after samples were processed for E. coli O157:H7 to obtain ingredient composition of diets fed during the finishing phase of sampled cattle. These data were used to evaluate potential associations between fecal, hide and carcass presence of E. coli O157:H7 and the feeding of distiller's grains to cattle. Data obtained regarding the inclusion of DG was diverse; feedlots varied in the form of DG fed to cattle (truckloads were fed wet DG, n = 12; dried DG, n = 2; both wet and dried DG, n = 3; unknown form, n = 1), the inclusion level (range = 3 to 40%), and the basis of inclusion level (dry matter vs. as fed). Truckloads of cattle fed diets either with or without DG also were not represented equally on all sampling days. No differences were seen in the high-shedder, enrichment-fecal, hide, or carcass prevalence of E. coli O157:H7 between the two diet designations evaluated in this study. Unfortunately, uncontrolled potential confounding variables such as sampling day may have limited our ability to accurately describe the relationship. In addition, we had tremendous variability in the type (wet versus dry) and inclusion level of distiller's grains, factors that may affect E. coli O157:H7 shedding. Because only five of ten collection days contained truckloads of cattle fed diets with and without distiller's grains and there was variability in the level and type of distiller's grains fed, our power to demonstrate a difference may have been limited. Statistical models estimating the probability of a high-shedder, enrichment-fecal, hide, or carcass sample to be positive for E. coli O157:H7, given finishing diet (with or without DG) would not converge if sampling day was included; thus, the unconditional results we obtained may not truly reflect the distiller's grains association and should be interpreted with caution. PARTICIPANTS: Investigators: Nagaraja, T. G., Dave Renter, Megan Jacob, Mike Sanderson, and Dan Thomson: T. G. Nagaraja: Microbiologist; Principal investigator; involved in all planning and decision making processes, managing funds, and overseeing laboratory analysis and reporting of results. David Renter: Epidemiologist; Co-Principal investigator; Responsible for the study design and statistical analysis; Also involved in all planning and decision making processes and overseeing laboratory analysis and reporting of results. Megan Jacob: Ph. D student; Graduate student coordinating sample collection and processing in laboratory, recording of data, and analysis of results. Mike Sanderson: Epidemiologist; Involved in the study design and statistical analysis. Dan Thomson: Feedlot nutritionist; Involved in setting up field studies. Dr. Kelly Lechtenberg, Director of Research, Midwest Veterinary Services, Oakland, Nebraska. Responsible for the field study conducted in Nebraska; Coordinated the purchase, handling, feeding and management of cattle at the feedlot. Laboratory technicians: Xiaorong Shi and Neil Wallace: Xiaorong Shi: Responsible for bacteriological procedures and molecular analyses (PCR and PFGE typing of isolates). Neil Wallace: Responsible for bacteriological procedures, ordering supplies, maintaining inventory and supervising undergraduate students. Graduate students: Ph. D. students: Charles Dodd, Trent Fox, Zac Paddock. MPH students: Ethel Taylor. M. S. Students: Shelby Reinstein, Callie Walker. Graduate students are responsible for sample collection and processing in laboratory, recording of data, analysis of results, conference presentations and manuscript writing. Undergraduate students: A number of graduate students work part time in the laboratory. The students are trained in laboratory safety and analytical skills. The students presently working in the laboratory are: Blair Wyrick, Samantha Smith, Cody Strodtman, Katie Flock, Kristina Wert, Nick Reams, and Eric Haney. TARGET AUDIENCES: Scientists, Veterinarians, Food Safety Inspection Agency, Cattlemen, Packers, Students. The results from this study will be useful for the beef cattle, corn, and distiller's grains industries, as well as academic and governmental entities researching E. coli O157:H7. PROJECT MODIFICATIONS: No major modifications have been made to this project. The sample size was decreased to meet budget requirements. The number of pens was decreased from 84 to 70, and the number of cattle per pen was decreased from 15 to 12. The number of treatments was decreased from 7 to five (10% of wet and dried DG treatments were not used, however 20% and 40% of both wet and dried DG were maintained). It is not expected that these modifications will alter our ability to meet the objective, and sample size calculations were evaluated to ensure proper power would be retained to find treatment differences.
Impacts
The food supply in the United States is one of the safest in the world; however, food-borne illnesses do occur and frequently are associated with foods derived from animal agriculture. Escherichia coli O157:H7 and other Shiga toxin-producing E. coli (non-O157 serotypes) are important food-borne pathogens that cause hemorrhagic colitis, hemolytic uremic syndrome and thrombocytopenic purpura in humans. Besides food, there are other modes of transmission such as direct contact with cattle (farm workers, farm visitors, children visiting fairs and petting zoos), exposure to contaminated drinking and recreational water, and consumption of contaminated vegetables and fruits. Despite rigorous surveillance of meat processors by the USDA Food Safety and Inspection Service following the 1994 regulatory declaration of E. coli O157:H7 as an adulterant in raw ground beef, the number of confirmed human illnesses caused by E. coli O157:H7 continues at unacceptable levels. Control strategies aimed at reducing the prevalence and concentration of E. coli O157:H7 in cattle feces, thus reducing the overall number of bacteria entering both the food and environmental pathways, may be the most effective approach for reducing the overall risk of human infections. Furthermore, effective control of E. coli O157:H7 in the beef food supply chain will require knowledge on the ecology of the organism in cattle and cattle operations. Diet is one of the major factors affecting prevalence of E. coli O157:H7. Because distiller's grains are widely used as a cattle feed, it is important to determine their impact on prevalence of E. coli O157:H7 in cattle and subsequent contamination of carcasses. The information is useful to the cattle industry and provides an opportunity to modify diets to reduce the prevalence and pathogen load in cattle presented for slaughter.
Publications
- No publications reported this period
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