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 of target pathogens
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 form each positive sample for subsequent molecular subtyping and perform chemical analyses on food samples as appropriate.
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. To assist in accomplishing these objectives, the USDA, ARS has entered into a Specific Cooperative Agreement (SCA) with Drexel University. In Phase I of this SCA, we purchased 7944 samples of food from retail establishments in FoodNet sites in California, Maryland, Georgia, and Connecticut between December 2012 and February 2012. Food categories sampled included: smoked seafood (748), seafood salad (738), low acid cut fruits (1362), soft cheese (2029), deli salads (non-meat; 1349), raw milk (326), and sandwiches (1392). 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 observed prevalence ranged from ca. 0% to 1.0% for seven product categories. For the 39 samples testing positive during screening, Lm levels ranged from ca. <0.3 cells/g as estimated statistically to 251 cells/g. 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.