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Foodborne Pathogen Persistence: From Identification of Risk Factors to Communication of Control Strategies


This proposed project will integrate applied research and outreach education to (i) gain a more comprehensive understanding of pathogen persistence, including transmission dynamics of persistent strains within food processing plants and risk factors associated with cross-contamination of foods by persistent strains (ii) populate and promote the utilization of a publicly available database that permits anonymous deposition of subtype, source and temporal data for key foodborne pathogens, to facilitate identification and surveillance of foodborne pathogen strains that persist in a food processing plant and (iii) develop and deliver outreach training sessions (i.e., in-plant trainings, webinars, workshops and symposia) to augment knowledge regarding pathogen persistence, as well as to communicate risk factors for cross-contamination of food products by persistent strains and mitigation strategies to control pathogen persistence. <P>

In order to achieve the goals above the following specific research objectives will be completed: Obj. I. Perform longitudinal studies in meat and seafood processing plants to detect L. monocytogenes, Salmonella and pSTEC in the plant environment and food products. Obj. II. Subtype isolates from Obj. I to identify persistent strains, elucidate persistent strain transmission dynamics, including risk factors for persistence and cross-contamination of food products. Obj. III. Extend knowledge regarding persistence of pathogens in food processing plants, including risk factors for persistence and mitigation strategies to control persistent strains. Upon completion of Obj I., we will have tested approximately 3,600 samples, including environmental and food product samples, from at least 12 different food processing plants, including fresh meat, RTE meat and RTE seafood processing plants, to isolate and detect L. monocytogenes, Salmonella and pSTEC. In addition, we will have collected data regarding plant demographics, production and sanitation practices through completion of a standardized questionnaire. Upon completion of Obj. II, we will have characterized L. monocytogenes, Salmonella, pSTEC isolates from food products and their associated processing environments from Obj. I by serotyping and PFGE typing. Patterns from PFGE typing will be deposited into the PathogenTracker database so that plants enrolled in this study can monitor contamination patterns within their plant. We will have conducted mathematical modeling to probe associations between plant factors and persistence of pathogens in the plant environment. After completion of Obj. III, we anticipate that we will have (i) conducted at least two one-day "Train-the-trainer" and industry workshops, (ii) organized at least two symposium on pathogen persistence at national or international meetings, and (iii) held at least one Webinar series. In addition, we will have developed and distributed training materials on pathogen persistence to a variety of outreach and extension personnel, allowing them to conduct additional training session and workshops based on the materials developed through this workshop.

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NON-TECHNICAL SUMMARY: More than 1,000 of 1,800 deaths caused by known foodborne pathogens in the U.S. each year can be attributed to Escherichia coli O157, Listeria monocytogenes, and Salmonella. ?DNA fingerprinting? or molecular subtyping differentiates isolates beyond the species and serotype level and molecular subtyping is routinely used to monitor foodborne pathogen transmission. Multistate outbreaks of foodborne illness linked to cross-contamination of foods by L. monocytogenes or Salmonella strains that persisted in the plant environment for extended periods highlight the continued need for research and training on L. monocytogenes persistence and knowledge gaps regarding Salmonella and E. coli O157 persistence. The overall goal of this project is to integrate applied research and outreach to augment knowledge regarding foodborne pathogen persistence. Combined field studies and molecular subtyping will be performed to identify L. monocytogenes, Salmonella and E. coli O157:H7 strains that persist in the plant environment to probe risk factors and pathogen phenotypes that may contribute to persistence. In order to accomplish this overall goal, we will (i) conduct longitudinal studies in fresh meat, RTE meat and smoked seafood processing plants to isolate L. monocytogenes, Salmonella and E. coli O157 from the plant environment and associated food products, (ii) subtype isolates to identify persistent strains, elucidate persistent strain transmission patterns and identify risk factors for persistence, (iii) compare the ability of persistent and transient strains representing each target pathogen to adhere to food contact surfaces and resist sanitizers and (iv) extend knowledge regarding persistence of pathogens in the plant environment, including risk factors and mitigation strategies to control persistence. Knowledge gained will be disseminated to food processors and trainers through a series of outreach activities designed to provide fundamental knowledge regarding (i) pathogen persistence, (ii) identification of persistent strains and monitoring transmission patterns and (iii) risk factors for persistence and mitigation strategies. <P>APPROACH: At least four plants belonging to each of the following types of food processing plants; fresh meat, RTE meat and RTE seafood will be identified and enrolled in this project. The identity of food processing plants enrolled in this study will remain confidential. During an initial site visit to each plant, researchers will construct maps of the layout of each plant, including diagrams of overall product and employee traffic flow, select environmental sample sites and administer a standardized questionnaire to collect data on plant demographics, production and sanitation procedures (see appendix 1). Routine sample collections will be performed at each plant on a bi-monthly basis. We will perform pulsed field gel electrophoresis (PFGE) typing of L. monocytogenes, Salmonella and pSTEC isolates following standard CDC PFGE protocols and deposit PFGE pattern data and associated epidemiological information in the publicly available WWW-based PathogenTracker database. Through our efforts to extend knowledge on pathogen persistence, our team will also train food industry personnel responsible for food safety on the use of PathogenTracker database as a tool to monitor in-plant pathogen contamination patterns. We will also compare data from plant survey questionnaires to the nature of persistent colonization of each plant by the pathogens targeted in this study along with contamination patterns for each plant to identify risk factors for persistence and mitigations to control persistence. The project team will (i) communicate testing and molecular subtyping results to each plant enrolled in this study and conduct in-plant training sessions to critically evaluate contamination patterns in each plant, (ii) develop short fact-sheets on pathogen persistence in food processing plants, (iii) conduct a web-based seminar (webinar) series to provide information on pathogen persistence in processing plants and (iv) develop and deliver workshops and symposia targeted towards industry and trainers, providing information on pathogen persistence.<P>
PROGRESS: 2011/11 TO 2012/11<br/>
OUTPUTS: Two fresh meat plants and two ready-to-eat meat plants in Colorado along with two ready-to-eat seafood plants in upstate New York were enrolled in a longitudinal study and the first phase of this longitudinal study was completed. The purpose of the first phase of this longitudinal study was to determine baseline the prevalence of key human foodborne pathogens, including Listeria monocytogenes, Salmonella and Escherchia coli for the four meat plants and L. monocytogenes for the two seafood plants. Approximately 50 environmental sponge samples and a pooled raw and finished product sample were collected from each plant on a monthly basis for four to six months. Data from the initial phase of this longitudinal study were used to develop in-plant training modules and fact-sheets, including evaluation materials, to identify and interventions to eliminate harborage sites and practices that may contribute to cross-contamination of the finished product by the plant environment. In -plant trainings were completed and targeted interventions were recommended to each plant to control Listeria. The second phase of this longitudinal sampling study was to measure the impact of interventions through intensive pre- and post-operation sampling plans was also completed. Vector sampling to determine the directionality of contamination patterns leading to the establishment of harborage sites was completed. PARTICIPANTS: Texas Tech University University; Kendra Nightingale and Alex Brandt Cornell University; Martin Wiedmann, Thomas O'Malley, Matthew Stasiewicz, Sherry Roof, Steven Warchocki, Yrjo Grohn Colorado State University: Marissa Bunning and Eva Borjas TARGET AUDIENCES: Target audiences include other academic researchers as well as industry and government agencies that use combined testing and molecular subtyping to probe contamination patterns and elucidate transmission dynamics of foodborne pathogens in food processing plants to identify and eliminate harborage sites and practices that facilitate cross-contamination of the finished product by the plant environment. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.<P>

IMPACT: 2011/11 TO 2012/11<br/>
More than 5,000 samples were collected from meat and seafood plants enrolled in the study. Samples were microbiologically analyzed to detect important foodborne pathogens, including Listeria monocytogenes, Salmonella, and pathogenic shiga toxin encoding Escherichia coli. Isolates have been stored at either Cornell or Colorado State University and have been characterized by phenotypic (serotyping) and/or molecular subtyping (i.e., Pulsed field gel electrophoresis or ribotyping). Statistical approaches were developed and implemented to define environmental sites that persistently harbored the same Listeria molecular subtype. Findings from sample collections efforts, characterization of pathogen isolates and statistical analyses will be submitted as abstracts to be presented at a scientific meeting in 2013 (e.g., International Association of Food Protection or American Society for Microbiology) and presented in outreach training programs for small meat and seafood processing plants.

Wiedmann, Martin ; Nightingale, Kendra
Texas Tech University
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