A Large-Scale Survey of Retail Ready-to-Eat Foods for Listeria - - PowerPoint PPT Presentation

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A Large-Scale Survey of Retail Ready-to-Eat Foods for Listeria - - PowerPoint PPT Presentation

Nov 11, 2023 570 likes •814 views

A Large-Scale Survey of Retail Ready-to-Eat Foods for Listeria monocytogenes in the USA Jenny Scott National Food Processors Association Why? Industry desired to change US policy zero tolerance Ready-to-eat foods containing

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A Large-Scale Survey of Retail Ready-to-Eat Foods for Listeria monocytogenes in the USA

Jenny Scott National Food Processors Association

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Why?

  • Industry desired to change US policy –

“zero tolerance”

  • Ready-to-eat foods containing detectable levels

deemed adulterated

  • Recognized the need for a risk

assessment to set appropriate risk management strategies

  • Determined that lack of data (prevalence

and numbers) was impediment to conducting the needed risk assessment

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Project Objectives

1) Quantify the levels of Lm in certain foods in order to estimate actual consumer exposure to the organism 2) Identify the subtypes of Lm in those foods and compare them with the clinical subtypes from the same geographic area

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Project Objectives

3) Use the quantitative exposure data with illness data collected among consumers in the same geographic region to conduct a risk assessment to determine the impact of the number of Lm consumed on the risk of listeriosis

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NFPA RF-Listeria Project

  • The project team

– David Gombas, Yuhuan Chen, Jenny Scott et al. – expert consultations – industry, FDA, FSIS, Health Canada

  • Overall objective: obtain data to support

science-based policies

  • Retail survey and risk assessment

– 3 yr/$1.4 M project

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Approach

ÿ Collect data on Lm populations in retail foods likely to contribute to consumer exposure – products with relatively high Lm prevalence – products frequently consumed in test location – products not likely to be further treated

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Approach

ÿ Perform data collection in location where illness data are reliable

– CDC active surveillance for Lm in FoodNet Sites – Case control studies planned for 2000- 2001 – Clinical isolates could be available for subtyping

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Approach

ÿSelected sliced luncheon meats (ham, bologna, poultry) and prepared “deli” salads (e.g., potato, tuna) ÿSelected Northern California and Maryland

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Number of Samples

  • Determined statistically
  • Large numbers (2500-10,000)

needed to give 95% confidence of actual percentage positive

  • Trade off between the desired

confidence in the estimate and what was practical

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Products Collected and Tested

January 2000 – November 2001

  • Luncheon Meats (e.g., sliced

ham, bologna, poultry)

  • Deli Salads (e.g., tuna, potato,

pasta, coleslaw)

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Products Collected and Tested

October 2000 – November 2001

  • Fresh Soft Cheeses (e.g., queso blanco)
  • Bagged, Precut Leafy Vegetable Salad
  • Blue-veined and Soft Mold-ripened

Cheese (BVMRC)

  • Seafood Salads (other than tuna)
  • Smoked Seafood

(To develop exposure data for FDA Lm risk assessment)

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100 or 25 samples per category/site/week

Project Protocol

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Prevalence, Enumeration tests

  • Detection sensitivity: 1 cfu Lm in 25 gm
  • Enumeration range: 0.3 – 3x105/gm

Data reported to NFPA:

  • +/- for each sample, by product type and

FoodNet site

  • Lm levels in Lm-positive samples
  • Additional information for FDA samples

Lm isolates archived for subtyping: – Ribotyping, lineage (Cornell Univ.)

– PFGE, serotype (USDA ARS)

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Results of the Retail Survey

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Summary of Results Summary of Results

  • Prevalence of Lm was generally low

– 577 positive of 31,705 samples (1.82% prevalence) – 0.2-4.7%

  • Numbers of Lm were generally low

– In 402 of the 577 positive samples the numbers were <0.3 MPN/g

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31,705 Samples Tested in 2000-2001

MD CA MD+CA

Fresh Soft Cheese

4 (1450) 1 (1481) 5 (2931)

Bagged Salads

8 (1465) 14 (1501) 22 (2966)

BVSMR Cheese

7 (1473) 30 (1497) 37 (2970)

Seafood Salads

88 (1225) 27 (1221) 115 (2446)

Smoked Seafood

43 (1281) 71 (1363) 114 (2644)

Luncheon Meats

54 (4599) 28 (4600) 82 (9199)

Deli Salads

103 (4293) 99 (4256) 202 (8549)

  • No. Positives (No. Samples Tested)

Products

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1 2 3 4 5

0.2 0.7 1.3 4.7 4.3 0.9 2.4 NFPA RF

% positive

F r e s h S

  • f

t C h e e s e Bagged Salad BVSMR Cheese S e a f

  • d

S a l a d S m

  • k

e d S e a f

  • d

Luncheon Meat D e l i S a l a d

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20 40 60 80 100 120 140 160 180 <0.3 0.3-10 >10-100 >100

Contamination Levels of Lm When Detected

FS Ch BS BV Ch SS Sm S L M DS

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1 2 3 4 5 6 7 8 9 >10-100 >100

Contamination Levels of Lm When Detected

FS Ch BS BV Ch SS Sm S LM DS

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Publications: JFP 66(4): 559- 569 and 570-577. 2003

  • 1. Survey of Listeria monocytogenes

in Ready-to-Eat Foods

David Gombas, Yuhuan Chen, Rocelle Clavero, Virginia Scott

  • 2. Listeria monocytogenes: Low

Levels Equal Low Risk

Yuhuan Chen, William Ross, Virginia Scott David Gombas

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Next Step: Dose-Response in Relation to Genetic Subtypes

  • Ribotype, Lineages (Cornell Univ.),

PFGE, serotype (USDA ARS)

– Prevalence/concentration in food isolates – Prevalence in human isolates

  • Use subtype and enumeration data

– Subtype-specific risk assessment

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Acknowledgements

  • Funding

– USDA CSREES, – FDA (JIFSAN) – Industry partners

  • Technical assistance

– William Ross – Robert Blodgett, Jerome Schneidman Wallace Garthright