1. 1st International Conference on Microbial Risk Assessment: Foodborne Hazards, College Park MD, July 2002 1 of 19 Modeling Cross-contamination in Quantitative Microbial Risk Assessment Don Schaffner Food Risk Analysis Initiative Rutgers University

2. 1st International Conference on Microbial Risk Assessment: Foodborne Hazards, College Park MD, July 2002 2 of 19 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

3. 1st International Conference on Microbial Risk Assessment: Foodborne Hazards, College Park MD, July 2002 3 of 19 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

4. 1st International Conference on Microbial Risk Assessment: Foodborne Hazards, College Park MD, July 2002 4 of 19 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

5. 1st International Conference on Microbial Risk Assessment: Foodborne Hazards, College Park MD, July 2002 5 of 19 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?

6. 1st International Conference on Microbial Risk Assessment: Foodborne Hazards, College Park MD, July 2002 6 of 19 Data Analysis Log transformation of % transfer Frequency histogram in Excel Best distribution using BestFit Normal distributions fit the data

7. 1st International Conference on Microbial Risk Assessment: Foodborne Hazards, College Park MD, July 2002 7 of 19 Think about data transformation…

8. 1st International Conference on Microbial Risk Assessment: Foodborne Hazards, College Park MD, July 2002 8 of 19 Cross contamination results

9. 1st International Conference on Microbial Risk Assessment: Foodborne Hazards, College Park MD, July 2002 9 of 19 Glove barrier: Chicken to hand

10. 1st International Conference on Microbial Risk Assessment: Foodborne Hazards, College Park MD, July 2002 10 of 19 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.

11. 1st International Conference on Microbial Risk Assessment: Foodborne Hazards, College Park MD, July 2002 11 of 19 Currently ongoing research with application on microbial behavior in the kitchen environment

12. 1st International Conference on Microbial Risk Assessment: Foodborne Hazards, College Park MD, July 2002 12 of 19 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.”

13. 1st International Conference on Microbial Risk Assessment: Foodborne Hazards, College Park MD, July 2002 13 of 19 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

14. 1st International Conference on Microbial Risk Assessment: Foodborne Hazards, College Park MD, July 2002 14 of 19 Non-linear process

15. 1st International Conference on Microbial Risk Assessment: Foodborne Hazards, College Park MD, July 2002 15 of 19 Model interface

16. 1st International Conference on Microbial Risk Assessment: Foodborne Hazards, College Park MD, July 2002 16 of 19 High Rate Results initial: 1000 storage increase: 1 cooking decrease: 5 log cross contamination rate mean: -1 (10%) log cross contamination standard deviation: 1

17. 1st International Conference on Microbial Risk Assessment: Foodborne Hazards, College Park MD, July 2002 17 of 19 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

18. 1st International Conference on Microbial Risk Assessment: Foodborne Hazards, College Park MD, July 2002 18 of 19 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

19. 1st International Conference on Microbial Risk Assessment: Foodborne Hazards, College Park MD, July 2002 19 of 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