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United States Department of Agriculture

Agricultural Research Service

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Location: Food Safety and Intervention Technologies Research

2012 Annual Report

1a. Objectives (from AD-416):
Quantify the occurrence of foodborne pathogens in select foods: a.) Screen foods for the presence/absence of target pathogens. b.) Determine levels of target pathogens in selected foods. c.) Subtype multiple isolates from each positive sample. d.) Conduct proximate composition analyses on selected foods.

1b. Approach (from AD-416):
Work with FDA, USDA/ARS, and USDA/FSIS and associated industry partners to collect/purchase targeted food samples from retail establishments. Test samples for presence/absence of target pathogens, determine the levels of the pathogen(s) in each positive sample by direct plating or enrichment. Retain multiple isolates from each positive sample for subsequent molecular subtyping and perform chemical analyses on food samples as appropriate.

3. Progress Report:
Listeria monocytogenes (Lm) is a facultative intracellular bacterium that is the causative agent of listeriosis. It is one of the most virulent foodborne pathogens, with 20 to 30 percent of clinical infections resulting in death, and is one of the top five leading causes of death among foodborne pathogens. Over the past decade, the Federal government has focused significant resources on reducing foodborne illness from ready-to-eat (RTE) foods. However, despite these efforts, foodborne illness caused by Listeria monocytogenes (Lm) and associated with RTE foods continues. The Food and Drug Administration (FDA), the USDA, Food Safety and Inspection Service (FSIS), and the USDA, Agricultural Research Service (ARS) have an interest in obtaining more current information on the association of Lm (i.e., rates, amounts, and subtypes) with RTE foods to evaluate the relative public health risk. This information is essential for both Agencies to effectively allocate resources to mitigate public health risks associated with Lm. Thus, USDA-FSIS provided funding to the United States Department of Agriculture, ARS, to partially support a study on the analysis of food samples collected at retail to determine the prevalence, levels, and subtypes of Lm associated with RTE foods. To assist in accomplishing these objectives, the USDA, ARS has entered into a Specific Cooperative Agreement (SCA) with Drexel University. As part of this Interagency agreement, to date we have purchased about 6000 samples of food from retail establishments in FoodNet sites in California, Maryland, Georgia, and Connecticut between July of 2011 and June 2012. Food categories sampled included: deli meat salads, deli meats, and dry/fermented sausage. Samples were analyzed using the FDA-BAM method, which included screening (25 gram or ml per each sample) and enumeration of positive samples by the MPN method and direct plating. The prevalence data for these FSIS-regulated products are currently being analyzed; however, Lm levels ranged from ca. less than 0.3 to 110 cells/g as estimated statistically. This is the most comprehensive survey of Lm in retail RTE foods in the past decade. Our findings provide data to assess changes in Lm prevalence and levels in RTE foods and will be used to update the 2003 Interagency Lm risk assessment. The study also underscores the importance of continued research to develop and validate interventions to ensure a wholesome food supply.

4. Accomplishments

Last Modified: 2/23/2016
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