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NFPA Survey on L. monocytogenes in Ready-to-Eat Foods

NFPA Survey on L. monocytogenes in Ready-to-Eat Foods. Yuhuan Chen, Jenny Scott National Food Processors Association Research Foundation. Publication: JFP 66(4) 2003. Survey of Listeria monocytogenes in Ready-to-Eat Foods David Gombas, Yuhuan Chen, Rocelle Clavero, Virginia Scott.

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NFPA Survey on L. monocytogenes in Ready-to-Eat Foods

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  1. NFPA Survey on L. monocytogenes in Ready-to-Eat Foods Yuhuan Chen, Jenny Scott National Food Processors Association Research Foundation

  2. Publication: JFP 66(4) 2003 • Survey of Listeria monocytogenes in Ready-to-Eat Foods David Gombas, Yuhuan Chen, Rocelle Clavero, Virginia Scott

  3. Initiation of Study • Risk management decision • Funding from nine industry partners through NFPA • Seek strategy effective in reducing listeriosis • Is there an alternative to “zero tolerance”? • Seek more than one strategy to solve the problem • “Listeria monocytogenes: low levels equal low risk” JFP 66(4) Yuhuan Chen, William Ross, Virginia Scott, David Gombas

  4. Project Objective • Develop data relative to the risk of listeriosis to support science-based strategy for addressing L. monocytogenes in foods

  5. Study Design • Product selection • Number of samples • Sampling site selection • Sampling location within FoodNet sites • Selection of retail stores within counties • Other aspects • Handling of samples, testing lab selection, testing methods

  6. Product Selection • Retail foods likely to contribute to consumer exposure • Products with relatively high prevalence • Products frequently consumed • Products not likely to be further treated

  7. Product Categories January 2000 – November 2001 • Luncheon Meats (ham, bologna, poultry) • Deli Salads (potato, tuna, pasta, cole slaw) October 2000 – November 2001 • Bagged, Precut Leafy Vegetable Salads • Blue-veined Cheeses • Fresh Soft Cheeses • Soft Mold-ripened Cheeses • Seafood Salads • Smoked Seafood

  8. Number of Samples • Considerations • Prevalence thought to be low (< 5%) • Cost for enumeration high • Assistance from FDA to estimate total number of samples needed

  9. Sampling Site Selection • Areas where illness data are reliable • CDC active surveillance for listeriosis in FoodNet Sites • Case control study conducted • Selected two FoodNet sites widely separated • northern California • Maryland

  10. Estimate of Total Number of Positive Samples n: total number of positive samples P: percent positive for the population d: desired upper bound on absolute error z: 1.96, 95% confidence level

  11. Estimate of Number of Samples • Assume P=50% • Given value of percentage unknown • Conservative • n=125, 250, 500; d=8.8, 6.2, 4.4% • Total number of samples 2500, 5000, 10,000 • assuming 5% prevalence

  12. Total Number of Samples: Luncheon Meats and Deli Salads • Initial plan • 2500 samples per product per FoodNet site • Two products: luncheon meats, deli salads • Two sites: MD and CA • 5000 samples per product • 10000 samples total • Actual collection doubled • Prevalence considerably lower than expected

  13. Sampling Locations in FoodNet Sites • Northern CA • Alameda and San Francisco counties (counties in the FoodNet site) • Maryland • Five counties plus Baltimore City (FoodNet site) • Total 10 counties plus Baltimore City • All counties containing > 2% of population (listeriosis reporting statewide) • Samples weighted by populations in county or city

  14. Sampling RTE Foods • In proportion to consumption • Luncheon meats and deli salads • Frequency of consumption within the geographical area based on CSFII • West for CA, South for MD • Example, luncheon meats ham-bologna-turkey/chicken • 50%-30%-20% in MD • 43%-30%-27% in CA

  15. Sampling RTE Foods • 100 samples per week for luncheon meats or deli salads • 75% from List A stores (major super markets) • 25% from List B stores (other grocers) • 25 samples per week for each of six categories • At least two List A and at least two List B stores • Supplementary lists of stores used as needed

  16. FOOD SAMPLE Divide into Two Portions Screening Enumeration Composite Positive, test individuals Composite Negative, Stop Direct plating (OXA or MOX) MPN* (UVM-Fraser or BLEB) If positive, proceed to Enumeration Confirmation L. monocytogenes isolate * 9-tube MPN: 1.0-0.1-0.01 g

  17. 31,707 Samples Tested in 2000-2001

  18. Lessons from the Study • Resource intensive • Three years/1.4 M • Industry support, government funding • Team effort • Jenny Scott, David Gombas, et al. • Outside contractors for sample collection and analysis • Expert consultations • Meetings with Agencies • Understand regulatory concerns • Seek feedback about study design and approaches

  19. Lessons from the Study • Industry concerns to be addressed • Confidentiality issues • Issues with unfavorable regulatory attention • Not identify ham, bologna, or chicken/turkey • Samples collected by third party

  20. Lessons from the Study • More information • Packaging location • Store vs. manufacturer • Did not design sampling accordingly to sale or consumption • Enumeration data • An opportunity to leverage industry and government resources • Started study with two categories • Obtained funding from JIFSAN to collect data on six additional categories

  21. Acknowledgements • Funding • Funding from industry partners through NFPA • USDA CSREES, FDA (JIFSAN) • Technical assistance • Robert Blodgett • Jerome Schneidman • Wallace Garthright

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