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United States Department of Agriculture

Agricultural Research Service

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Location: Warmwater Aquaculture Research Unit

2012 Annual Report

1a. Objectives (from AD-416):
Research will address methods to determine the presence of pathogens in catfish/catfish products and to maximize elimination methods. Detection techniques will be developed to aid in processing and packaging operations, which should further enhance product safety. Specifically the objectives are: Optimize safety of aquaculture products through innovative processes for reducing microbiological, physical and chemical hazards in seafood/aquaculture products. Determine the mechanisms influencing microbial survival of selected pathogens in seafood/aquaculture products. Optimize the market value of seafood/aquaculture products through enhanced food safety and quality.

1b. Approach (from AD-416):
Develop and evaluate methods for detection and reduction of microorganisms, toxins and contaminants that could affect the safety of seafood/aquaculture products.

3. Progress Report:
The Mississippi Center for Food Safety and Postharvest Technology’s objectives are to optimize safety and quality of aquaculture and seafood products, determine mechanisms influencing survival of pathogens in aquaculture and seafood products, and develop methods for identifying pathogens and factors affecting pathogen virulence. The center works with scientists across disciplines and aims at solving problems utilizing a holistic approach. About 25 scientists, 5 post-doctoral scientists, 6 doctoral candidates, 25 masters degree candidates, and many undergraduate students and collaborators have been a part of this project. One provisional patent, 80 journal publications, and more than 100 presentations, workshops, and outreach activities with high impact have been derived from this project. Work with industry, government and academicians as a result of efforts produced by this project have resulted in better and safer products for the U.S. consumer. Major accomplishments include the following: Listeria isogenic mutants delta lmo2117 and delta lmo2464 have been shown to be required for virulence. It was shown that lmo2464 is required for adhesion and invasion in macrophages and that lmo2464 also contributes to attachment and invasion in colonic epithelial cells. Gene lmo2117 also contributes to adherence in colonic epithelial cells. The persistence of Salmonella (S.) enterica serotype Kentucky on chicken litter (rice hulls) for 42 days at 30°C, and of S. enterica serotype Kentucky and Escherichia coli on refrigerated raw catfish fillets, boneless chicken fillets, and ground beef over 14 days was demonstrated through a bioluminescent technique developed. Biochemical techniques for enrichment of post-translationally modified proteins in chicken macrophages and ubiquitin-specific probe labeling of chicken macrophages was established. Red-eared sliders were confirmed being hosts for parasites that can infect fish and potentially catfish. DNA sequencing data generated has and will be used to detect all stages of many of these unknown larval nematode life cycles. A simple one-tube test for Salmonella detection and enumeration was developed and patented. A method for derivitization of nitrofuran metabolites in catfish tissue has been developed. Low levels of furazolidone and furaltadone in catfish tissue samples were identified. Phage P100 or LAE were shown to be listericidal whereas PL-SD was listeriostatic. These compounds were found to be very efficient in reducing Listeria (L.) monocytogenes counts by 2 to 3 log colony-forming units per gram and maintain during subsequent cold storage. Potassium acetate and lactate were not bactericidal but were bacteriostatic to Listeria over 14 days. Catfish frankfurters were produced using 50% catfish fillet nuggets, which add value to these low value raw materials. The frankfurters were very acceptable to consumers and were prepared to insure their safety. Minimum inhibitory concentrations for reduction of Vibrio (V.) parahemolyticus and Vibrio (V.) vulnificus in shucked, raw oysters were determined. A minimum exposure of 10 minutes at 60 to 400 parts per million were needed or 30 minutes at 40 to 300 parts per million, depending on antimicrobial.

4. Accomplishments

Last Modified: 06/23/2017
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