NFPA Survey on L' monocytogenes in ReadytoEat Foods

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

• Yuhuan Chen, Jenny Scott
• National Food Processors Association
• Research Foundation

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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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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

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Project Objective

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

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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

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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

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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

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Number of Samples

• Considerations
• Prevalence thought to be low (lt 5)
• Cost for enumeration high
• Assistance from FDA to estimate total number of
  samples needed

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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

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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
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Estimate of Number of Samples

• Assume P50
• Given value of percentage unknown
• Conservative
• n125, 250, 500 d8.8, 6.2, 4.4
• Total number of samples 2500, 5000, 10,000
• assuming 5 prevalence

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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

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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 gt 2 of population
  (listeriosis reporting statewide)
• Samples weighted by populations in county or city

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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

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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

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31,707 Samples Tested in 2000-2001
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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

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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

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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

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Acknowledgements

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