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Modeling Persistence of Non-O157 Shiga Toxin-Producing Escherichia Coli in Beef Slaughter and Validation of Interventions used in Processing


Objective 1. Comparatively model the persistence of non-O157 STEC and E. coli O157:H7 in relation to key process interventions in large and small beef abattoirs in order to answer the following question: Are non-O157 STEC more prevalent and/or persistent than E. coli O157:H7 in beef slaughter operations The results of these studies will allow us to develop models which will predict whether enhancement of existing intervention strategies is necessary in order to eliminate contamination from non-O157 STEC. An understanding of the persistence/prevalence of non-O157 STEC in the processing environment is critical to beef slaughter plants as they are called on to reassess their HACCP plans and pre-requisite programs due to the emergence of these pathogens. These results will allow us to identify factors which significantly impact the persistence and prevalence of non-O157 STEC in both small and large beef abattoirs as we develop methods for industry validation of intervention strategies (Objectives 2 and 3). <P>Objective 2. Comparatively evaluate the survival of non-O157 STEC and E. coli O157:H7 to stresses likely to be encountered in standard beef processing operations: interventions applied to subprimals and trim (organic acid wash), drying/smoking used in the manufacture of beef jerky, and heating/smoking used in the manufacture of frankfurters. Results from microbial modeling will inform this portion of our research as we attempt to identify and evaluate processing interventions against a wide array of representative non-O157 STEC. Our results will lead to recommendations that can be shared with the industry to ultimately improve the safety of the U.S. meat supply. The information obtained will allow us to assist processors in reassessing their HACCP plans, and in monitoring critical limits relative to this emerging public health threat. <P>Objective 3. Utilize pathogen surrogates (commercially available LAB and non-pathogenic E. coli) to develop methods for in-plant validation of standard interventions and processes against the most tolerant non-O157 STEC strains. The results of this work will allow the beef industry to reassess and validate HACCP plans in an effort to more effectively protect public health. Objective 4. Fully extend applied research findings to the meat industry, state and federal regulators, and university extension specialists. The results of this project will be shared with meat industry professionals, regulators, and extension specialists through web-based materials, and publications. We will develop training materials, and guidelines (where appropriate), which will educate processors and state and federal regulators on the use of surrogates for in-plant critical limit validation and we will evaluate the results of our efforts. The result of this project will allow meat industry personnel to appropriately reassess their HACCP plans to address the emerging threat to public health in the form of non-O157 STEC.

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NON-TECHNICAL SUMMARY: Progress has been made in reducing the incidence of key foodborne illnesses, with at least some of the decrease attributable to mandatory implementation of the Hazard Analysis Critical Control Point (HACCP) in the nation's meat, poultry, and seafood processing establishments. However, pathogenic Escherichia coli associated with beef slaughter and processing remains a concern. Information is surfacing that shiga toxin-producing E. coli (STEC) strains O26:[H11], O103:H2, O111:[H8] and O145:[H28], in addition to commonly recognized O157:H7, present a public health threat. Together, the serotypes O157, O26, O103, O111 and O145 are referred to as the gang of five. This integrated research and extension project will: 1)Develop models which compare the persistence and prevalence of O157 and non-O157 STEC in relation to key process interventions in beef slaughter operations; 2)Evaluate the effectiveness of standard beef processing interventions against non-O157 STEC: organic acid wash applied to subprimals/trim; thermal processing operations used in the manufacture of frankfurters and jerky; 3)Utilize surrogates (lactic acid bacteria and non-pathogenic E. coli) to develop methods for in-plant validation of critical limits against STEC; and 4)Fully disseminate research findings to stakeholders. This research will fill knowledge gaps which exist about the persistence/prevalence of STEC in beef processing operations, and will lead to the development of recommendations for controlling and eliminating these pathogens. These recommendations will be disseminated to large and small beef processing operations nationwide, which will implement them as part of their HACCP plan.


APPROACH: Samples will be collected at six different points during slaughter and dressing at 3 large beef abattoirs located in geographically distinct regions of the United States. Sixty samples will be collected at each of the 6 points; and samples will be divided equally throughout the year, so that 15 samples are taken at each sampling point during each season of the year. Samples will be collected at 3 different points during slaughter and dressing procedures representative of small beef abattoirs. A total of 540 samples will be collected and analyzed. Persistence and prevalence of non-O157 and E. coli O157:H7 will be established based on carcass sponge sampling and screening for the presence of serotypes O157, O26, O103, O111 and O145 (the gang of 5) using a multiplex realtime PCR. A microbial risk assessment model will be developed based on the prevalence and persistence of E. coli through the processing lines in abattoirs. From carcass sampling, 3 to 5 cultures each of the 4 most important non-O157 STEC serotypes that have been isolated from foods: O26, O111, O103, and O145 will be screened for intervention experiments. These 4 serotypes, along with a 12-strain high-tolerance E. coli O157:H7 inoculum will comprise the inoculum used in intervention studies. Seven lactic acid bacteria (LAB) starter cultures and 2 non-pathogenic E. coli cultures that have been shown previously to offer potential as pathogen surrogates will be evaluated as potential surrogate cultures. Intervention treatments used with subprimal cuts/trim (acid/water wash) will be evaluated; LAB and non-pathogenic E. coli strains (biotype I) will be evaluated as pathogen surrogates for potential use in in-plant validation. Inoculated cuts/trim will be subjected to standard acid or water wash treatments and reduction in pathogen and surrogate will be determined. Additionally, Salmonella and STEC will be inoculated into frankfurter batter or whole muscle beef jerky which is subsequently processed under commercial conditions. Additional LAB and biotype I-inoculated franks or jerky strips will also be processed. For each product (subprimal cut/trim/frankfurter/jerky strip), change in log CFU per sample between starting sample and post-intervention sample will be determined. Potential surrogates will be judged successful if they are not significantly different from the target pathogen(s) when subjected to a particular intervention. Appropriate surrogate organisms will be taken into collaborating plants for concept verification before research findings are published. This project will lead to the development of in-plant validation methods that will prove to be extremely useful to the industry. We will make available to processors information that is not only science-based but is applicable to their unique processing situation and will provide both processors and regulators with the assurance that they are doing their best to maintain the safety of the food supply.

Ingham, Barbara
University of Wisconsin - Madison
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