1 / 19

Modeling Cross-contamination in Quantitative Microbial Risk Assessment

Modeling Cross-contamination in Quantitative Microbial Risk Assessment. Don Schaffner Food Risk Analysis Initiative Rutgers University. The Achilles heel of risk assessment - G. Paoli 7/24/02. Modeling Cross-contamination in Quantitative Microbial Risk Assessment.

nico
Download Presentation

Modeling Cross-contamination in Quantitative Microbial Risk Assessment

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Modeling Cross-contamination in Quantitative Microbial Risk Assessment Don SchaffnerFood Risk Analysis Initiative Rutgers University 1st International Conference on Microbial Risk Assessment: Foodborne Hazards, College Park MD, July 2002

  2. The Achilles heel of risk assessment - G. Paoli 7/24/02 Modeling Cross-contamination in Quantitative Microbial Risk Assessment Don SchaffnerFood Risk Analysis Initiative Rutgers University 1st International Conference on Microbial Risk Assessment: Foodborne Hazards, College Park MD, July 2002

  3. Laboratory Experiments • Nalidixic acid resistant Enterobacter aerogenes with attachment characteristics similar to Salmonella • More than 30 participants dice inoculated chicken, wash hands and/or wear gloves, slice lettuce • Sample hands, foods, faucet spigots cutting boards for Enterobacter 1st International Conference on Microbial Risk Assessment: Foodborne Hazards, College Park MD, July 2002

  4. Why these studies ? • Practical consideration • A company was interested in showing efficacy of a touch-free faucet… they provided funding! • Our research philosophy • Variability matters, especially for modeling and risk assessment 1st International Conference on Microbial Risk Assessment: Foodborne Hazards, College Park MD, July 2002

  5. Things to think about… • A surface can either … • be sampled or • be used to contaminate another surface • Relative numbers and rates • Dirty hands -> clean faucet handles • Dirty hands <-> dirty faucet handles • Clean hands <- dirty faucet handles • How many observations at one set of conditions are needed? 1st International Conference on Microbial Risk Assessment: Foodborne Hazards, College Park MD, July 2002

  6. Data Analysis • Log transformation of % transfer • Frequency histogram in Excel • Best distribution using BestFit • Normal distributions fit the data 1st International Conference on Microbial Risk Assessment: Foodborne Hazards, College Park MD, July 2002

  7. Think about data transformation… 1st International Conference on Microbial Risk Assessment: Foodborne Hazards, College Park MD, July 2002

  8. Cross contamination results 1st International Conference on Microbial Risk Assessment: Foodborne Hazards, College Park MD, July 2002

  9. Glove barrier: Chicken to hand 1st International Conference on Microbial Risk Assessment: Foodborne Hazards, College Park MD, July 2002

  10. Our Published Work • Chen, Y., Jackson, K.M. Chea, F.P. and Schaffner, D.W. 2001. Quantification and variability analysis of bacterial cross-contamination rates in the kitchen. Journal of Food Protection. 64(1):72-80. • Montville, R., Chen, Y., and Schaffner, D.W. 2001. Glove barriers to bacterial cross-contamination. Journal of Food Protection. 64(6), 845–849. • Montville, R., Chen, Y. and Schaffner, D.W., 2002. Risk assessment of handwashing efficacy using literature and experimental data. International Journal of Food Microbiology 73(2-3), 305-313. 1st International Conference on Microbial Risk Assessment: Foodborne Hazards, College Park MD, July 2002

  11. Currently ongoing research with application on microbial behavior in the kitchen environment 1st International Conference on Microbial Risk Assessment: Foodborne Hazards, College Park MD, July 2002

  12. Other recent publications • L. L. Gibson, J. B. Rose, C. N. Haas, C. P. Gerba, and P. A. Rusin. Quantitative assessment of risk reduction from hand washing with antibacterial soaps. J.Appl.Microbiol. 92:136S-143S, 2002. • “The objective of this study was to examine the risk reduction achieved from using different soap formulations after diaper changing using a microbial quantitative risk assessment approach.” • T. A. Cogan, J. Slader, S. F. Bloomfield, and T. J. Humphrey. Achieving hygiene in the domestic kitchen: the effectiveness of commonly used cleaning procedures. J.Appl.Microbiol. 92 (5):885-892, 2002. • “Aims: To quantify the transmission of Salmonella and Campylobacter to hands, cloths, and hand- and food-contact surfaces during the preparation of raw poultry in domestic kitchens, and to examine the impact on numbers of these bacteria of detergent-based cleaning alone, or in conjunction with thorough rising.” 1st International Conference on Microbial Risk Assessment: Foodborne Hazards, College Park MD, July 2002

  13. Things to consider in QMRA • Cross-contamination must be handled differently than other increases • Two log increase due to growth: 1 + 2 = 3 • 100 CFU added from cross-contamination: 10 + 100 = 110 • Modeling the non-linear nature of the process 1st International Conference on Microbial Risk Assessment: Foodborne Hazards, College Park MD, July 2002

  14. Non-linear process 1st International Conference on Microbial Risk Assessment: Foodborne Hazards, College Park MD, July 2002

  15. Model interface 1st International Conference on Microbial Risk Assessment: Foodborne Hazards, College Park MD, July 2002

  16. initial: 1000 storage increase: 1 cooking decrease: 5 log cross contamination rate mean: -1 (10%) log cross contamination standard deviation: 1 High Rate Results 1st International Conference on Microbial Risk Assessment: Foodborne Hazards, College Park MD, July 2002

  17. Low Rate Results initial: 1000 storage increase: 1 cooking decrease: 5 log cross contamination rate mean: -3 (0.1%) log cross contamination standard deviation: 1 1st International Conference on Microbial Risk Assessment: Foodborne Hazards, College Park MD, July 2002

  18. Where to we go from here? • What factors are important in controlling transfer rate? • Soil type, organism, pressure, concentration, etc. • What routes are important? • Hand to mouth, cutting board to raw product, etc. • What behaviors are important? • Handwashing, cleaning frequency, etc. • Once we know what’s important, we can ignore what’s not important, and include a useful, simplified cross contamination module in our risk assessments 1st International Conference on Microbial Risk Assessment: Foodborne Hazards, College Park MD, July 2002

  19. Acknowledgements • Lee Budd for stimulating discussions • Sloan Valve company for support and funding • The Food Risk Analysis Initiative was funded in part by the New Jersey Agricultural Experiment Station • Members of the FoRAI team: Yuhuan Chen, Rebecca Montville, Kristin Jackson, Siobain Duffy, Purvi Vora, Lihui Zhao 1st International Conference on Microbial Risk Assessment: Foodborne Hazards, College Park MD, July 2002

More Related