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Reducing Incidences of Foodborne Disease through Preharvest Intervention, Postharvest Control, Molecular Tracking and Knowledge of the Biological Basis of Pathogen Function


The objectives of this proposal include: 1) Develop pre-harvest interventions for the produce and mushroom industry 2) Develop novel intervention methods to reduce pathogen prevalence in the food system 3) Develop novel molecular tracking systems for identifying pathogen transmission routes in the food system 4) Enhance understanding of the biological mechanisms promoting the survival and virulence of foodborne pathogens <P>Milestones and goals include: Objective 1: Collecting data on sanitizer trials that will assess the safety of produce irrigation water; quantification of the survival of human pathogens during mushroom composting and synthesis of recommendations for improving cleaning and sanitation protocols for facilities. Objective 2: Data collection to support recommendations for new packaging materials and non-thermal processing treatments to reduce the prevalence of pathogens on fresh meat and produce. Objective 3: Detection of novel epidemic clones of L. monocytogenes and E. coli through development of improved molecular subtyping methodologies; identify the routes of transmission of both pathogens within processing environments, especially those manufacturing ready-to-eat mushrooms; identification of new persistent strains of pathogens. Objective 4: Identification of the biological mechanism(s) promoting L. monocytogenes persistence within food processing environments; understand the evolutionary forces driving diversification of Shiga toxin-encoding bacteriophage and the impact this has on the ecology of Shiga toxin-producing E. coli from farm-to-fork.

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Non-Technical Summary:<br/>
Infectious diseases are one of the leading causes of death worldwide. In the U.S., foodborne pathogens are the greatest threat to food safety and are a growing problem due to the growing population of at-risk individuals and the emergence of new pathogens, many of which are also now resistant to multiple antibiotics. As a result of this emerging antibiotic resistance, prevention of infectious diseases increasing relies on preventing contamination. Much remains to be done to reach the national health objectives for foodborne- and healthcare-related illnesses. Enhanced measures are needed to reduce or prevent contamination in the food and healthcare system and to educate stakeholders more effectively about risks and prevention measures. Such measures can be better focused when the sources of human infections (i.e., animal reservoir species and transmission route) are known. Understanding of the routes of pathogen transmission requires the development of tracking methods that are capable of identifying organisms to the strain level. Once the ecology and spread within the food system is understood, principles of Hazard Analysis and Critical Control Points (HACCP) can be applied to identify pre-harvest and post-harvest control points, and to devise mechanisms for inactivating pathogens at these steps. Additionally, research directed at further understanding the biological basis of pathogen persistence along transmission routes is needed to devise evidence-based methods of decreasing the prominence of pathogens from farm-to-fork. Consumers are demanding safe foods, but at the same time they are demanding foods that are minimally processed with few or no food additives. This situation has created a major dilemma for the food industry, and highlights the need for practices and technologies that produce foods that are fresh and nutritious, but also free of pathogens. The project describes several key areas where faculty at Penn State's Department of Food Science will work collaboratively to develop improved methods of tracking and reducing pathogen prevalence throughout the food supply. Such an outcome would have tremendous benefits to food safety and public health in the U.S. and throughout the world.
Objective 1: A split-block design experiment will be used at the Horticultural Research Farm at Rock Springs, PA. Various disinfectants will be applied and we will analyze yield and coliform counts. Additionally, at the Penn State Univerisity Mushroom Research Center we will culture mushrooms using various composts and growing conditions. Standard microbiological methods will be followed to quantify pathogen prevalence.
<br/>Objective 2: Antimicrobial films containing nicin, colicin, and/or lysozyme will be prepared and observed for their ability to inhibit pathogen growth on meat surfaces using standard microbiological methods. Similar methods will be used to determine the effect of various antimicrobial dips on pathogen reduction on meat surfaces, and the impact of food processing conditions such as high pressure processing and pulsed light. Lastly, standard methods will be used to determine whether ultrasound can reduce pathogen prevalence on inoculated alfalfa seeds.
<br/>Objective 3: DNA sequencing and other molecular methods will be used to identify genomic regions of Listeria monocytogenes and Shiga toxin-producing Escherichia coli that are useful for separating unrelated isolates.
<br/>Objective 4: Standard methods will be used to evaluate the survival of Listeria monocytogenes during extended incubation and ability to persist within meat plant environments. DNA sequencing will be used to analyze the diversity within Shiga toxin-converting bacteriophage carried by E. coli O157:H7 strains.

Dudley, Edward; Knabel, Stephen; Cutter, Catherine; LaBorde, Luke; Doores, Stephanie
Pennsylvania State University
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