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Control of Food-Borne Pathogens in Pre- and Post-Harvest Environments


New methods to prevent, reduce or eliminate foodborne disease agents at all points of the food chain, from farm to fork, are needed to improve the safety of the food supply to prevent illnesses and deaths and to prevent economic losses to the food industry.<P> Objectives: <ul> <LI>Develop or improve methods for control or elimination of pathogens in pre-and post harvest environments including meat, poultry, seafood, fruits and vegetables and nutmeats. <LI>Develop and validate mathematical modeling to gain understanding of pathogen behavior in macro- and micro-environments.<LI> Investigate factors leading to the emergence, persistence and elimination of antimicrobial resistance in food processing and animal production environments. </ul>Outputs: <ul> <LI>Validated decontamination methods that can be used by the fruit, vegetable, seafood, meat and poultry industry to enhance the safety of their finished product <LI>Outreach/extension education and training materials for regulatory personnel, producers, processors, consumers, extension agents <LI>Overall enhanced food safety for consumers </ul>Outcomes or projected Impacts:<ul> <LI> Enhanced safety of fruit, vegetable, seafood, meat, and poultry products Increased understanding of food safety measures by regulatory personnel, producers, processors, consumers, extension agents <LI>Overall enhanced food safety for consumers </ul>Milestones: <BR>(2007): Pre-harvest food safety: Initiate work on antimicrobial films, high pressure processing of viruses. Modeling: Develop and validate wind tunnel to validate heat transfer models. Antimicrobial drug resistance: Tetracycline resistance genes in the environment. Total bacterial population genomic DNA extracted from fecal samples and analyzed for presence of all tetracycline resistance (Tc-R) genes.<BR> (2008): Pre-harvest food safety: Initiate efforts on sanitizers, high pressure processing of vibrios. Modeling: Collect growth data of Salmonella in chicken and beef at isothermal conditions. Develop neural network model and compare its performance to statistical models. Antimicrobial drug resistance: Environmental sample collection from antibiotic free and antibiotic receiving farms and molecular analysis. Analyze tetracycline resistant isolates for (expected) tetracycline resistance genes with PCR. <BR>(2009): Pre-harvest food safety: Investigate optimization of high pressure processing in RTE seafoods. Modeling: Collect growth data of E. coli in ground beef for different fat content at isothermal conditions. Antimicrobial drug resistance: Data analysis and manuscript preparation<BR> (2010): Pre-harvest food safety: Initiate outreach activities. Modeling: Current FSIS risk assessment model for E. coli in ground beef is based on models developed using broth. <BR>(2011): Pre-harvest food safety: continue outreach activities and publish research results. Modeling: Develop heat transfer to obtain temperature profile in shell eggs during cooling. <BR><BR>Expected Outputs: We hope to discover viable-but-non-culturable (VBNC)/stressed pathogens in food and environmental samples through the development of rapid and easy-to-use procedures.

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Non-Technical Summary: Salmonella is responsible for the largest number of outbreaks in the USA. However, source of illness remains a puzzle in many of the outbreaks. In many cases the source of illness is only speculated or arrived at by probability and not by complete identification. Another problem is that many food products that are imported or otherwise processed (frozen) that may contain Salmonella and other pathogens are not detected. The reason for this is that the pathogen may be in a nonculturable state, i.e., cannot be isolated utilizing normal culturing conditions. This affects our economy, including our state. The ability to have better, more reliable and sensitive methods to identify contaminated food products will allow us to compete more fairly in the global market and insure a safer food supply to the consumers. In addition, the ability to better identify sources of pathogens can help us pinpoint critical steps needed to produce safer food products. In specific, environmental (water, soil, manure, plant, and other samples) and food (fresh, frozen, etc) samples will be obtained (in some cases from collaborators/colleagues, in other cases from importers and distributors, in other cases by our group) and codified to be able to traceback the origins. These samples will then be split (keeping some in storage) and assayed for Salmonella and E. coli 0157:H7 by conventional (BAM, 2000; USDA, 2010) and unconventional methods (incubation for days without selective broth, incubation for days with selective broth, incubation with other nutrients, etc.) to determine the viability and recovery of pathogens. Once a pathogen is recovered as VNBC, then identification and typing will be done, in addition to confirmation by PCR. We will also check for patterns that are not common in that species (enzyme deficiency or other marker) to further study its survivability. Depending on the number of VNBC isolates and their source, we will then proceed to identify their genetic makeup (LSBI) to further identify characteristics of survivability. These isolates will then be exposed to different environmental conditions (pH, temperature, nutrients, etc) to discern their optimum growth characteristics to then design a proper recovery method. The method will then be validated with further samples. The method can then be used for epidemiological and related studies. <P> Approach: Since we recently found that nontyphoidal Salmonella spp. was resistant to culture in isolation on conventional nonselective/selective media including buffered peptone water, RV and tetrathionate broth, Brilliant green and XLD agar and PCR test, it is important to develop techniques to culture "unculturable Salmonella spp. on a novel recovery techniqu(s). Optimization for the growth of unculturable Salmonella spp. includes simulated natural environmental conditions including the need for specific nutrients, pH conditions, incubation temperatures or levels of oxygen in the atmosphere and a reliance on beneficial bacterial interactions within the source environment. Combinatorial approaches will also enhance optimization to improve isolation of unculturable pathogenic bacteria that can be cultured in the laboratory.

Kim, T J
Mississippi State University
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