Listeria monocytogenes transfer during slicing of delicatessen meats

1. Listeriamonocytogenes transfer during slicing of delicatessen meats Dr. Elliot Ryser Department of Food Science and Human Nutrition Michigan State University East Lansing, MI September 14, 2011

2. How Safe is Your Deli?

3. Not as Safe as You Think!

4. A Slicer Contaminated with Listeria Can Potentially Lead to Widespread Exposure

5. Listeriosis Outbreaks Traced to Delicatessen-Sliced Turkey May – Dec 2000: 16.9 million lbs recalled 29 cases 4 deaths 3 miscarriages June 2001: 16 cases of acute febrile gastroenteritis (no deaths) October 2002: 27.4 million lbs recalled 46 cases 7 deaths 3 miscarriages

6. Deadly Canadian ListeriosisOutbreak Linked to a Slicer - 2008

7. Predicted Annual Listeriosis Cases (Log Scale) from Different Food Categories in the United States (FDA/FSIS, 2003) DM = Deli meats ; FNR = Frankfurters (not reheated); P= Pâté and Meat Spreads; UM= Unpasteurized Fluid Milk; SS= Smoked Seafood; CR = Cooked Ready-To-Eat Crustaceans; HFD = High Fat and Other Dairy Products; SUC = Soft Unripened Cheese; PM = Pasteurized Fluid Milk; FSC = Fresh Soft Cheese; FR = Frankfurters (reheated); PF = Preserved Fish; RS = Raw Seafood; F = Fruits; DFS= Dry/Semi-dry Fermented Sausages; SSC = Semi-soft Cheese; SRC = Soft Ripened Cheese; V = Vegetables; DS = Deli-type Salads; IC= Ice Cream and Frozen Dairy Products; PC = Processed Cheese; CD = Cultured Milk Products; HC = Hard Cheese.

8. FSIS Regulatory Testing for L. monocytogenesin RTE Meats: 1990 - 2004 USDA Listeria Alternatives Implemented October 2003

9. Deli Meat Recalls, 1994 - 2005 12 Ham > 84 recalls Turkey > 53 million lbs 10 Chicken Beef Corned Beef 8 Other Number of recalls 6 4 2 0 1994 1995 1996 1997 1999 2000 2001 2002 2003 2004 2005 2006 Year

10. Deli Meat Recalls Including Prepared Sandwiches: 2006 - 2011

11. Deli Meat Surveys for Lm • Gombas et al., 2003 • 0.4% of manufacturer-sliced • 2.7% of delicatessen-sliced • Draughon et al., 2006 • 0.2% of manufacturer-sliced • 1.4% of delicatessen-sliced • Deli-sliced meat still 7 times more likely to be contaminated • Sales • 24.4% manufacturer-sliced • 75.6% delicatessen-sliced

12. Current Concerns ~ 1,600 listeriosis cases annually n including ~255 fatalities ~ 290 of 1,600 listeriosis cases from deli n meats: ~ 42 pre-sliced, ~ 248 deli-sliced ~ 46 fatalities from deli meats n ~ 6 fatalities from pre-sliced n ~ 40 fatalities from deli-sliced n

13. Points for Potential Listeria Contamination • Raw materials • Manufacture • Slicing • Food contact surfaces • Packaging • Retail • Slicing • Product handling • Deli environment • Consumer • Refrigerator • Slicing • Product handling • Environment Contamination primarily occurs after processing

14. Distribution of Listeria spp. in a Local Deli/Restaurant ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ LocationListeria L. seeligeri L. innocua L. mono ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ Basement 35 20 7 8 Kitchen 50 27 11 12 Front line 7 7 0 0 Sandwich line 20 9 8 3 Seafood case 5 0 5 0 Cheese case 9 4 5 0 Meat case 7 4 3 0 Display floor 10 3 2 5 Open back case 1 1 0 0 Board (meat, cheese) 10 1 9 0 Slicer (Hobart, sandwich line) 8 7 0 1 Slicer (Bizerba, deli) 5 4 0 1 Slicer (Bizerba, cheese) 2 2 0 0 Slicer (Hobart, basement sandwich line) 0 0 0 0 Slicer (Hobart), basement, cheese 1 1 0 0 ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------Total 170 90 50 30 ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

15. Distribution of Listeria spp. in a Local Deli/Restaurant _ Summary of 14 visits _________________________________________________ Location Listeria pos/ # of positive visits # tested (%) Listeria LM _______________________________________________________ Basement 35/70 (50) 13 4 Kitchen 50/84 (60) 14 6 Front line 7/42 (17) 4 0 Sandwich line 20/56 (36) 14 3 Cases(meat, cheese 42/154 (27) 13 5 floor, seafood) Slicer (H,SL) 8/70 (11) 4 1 Slicer 1(B,deli) 5/70 (7) 2 1 Slicer 2(B,deli) 2/70 (3) 1 0 Slicer 1/103 (1) 1 0 (Cheese, basement) Slicer 0/70 (0) 0 0 (meat, basement) _________________________________________________________________

16. Outline 1. Transfer of L. monocytogenes to different components of a deli slicer 2. L. monocytogenes transfer to deli meats during slicing 3. Impact of biofilm formation and sublethal injury on Listeria transfer to deli meats 4. Development of a risk assessment for L. monocytogenes in deli meat

17. Major Listeria Transfer Points on a Berkel Slicer Determined with Glo-GermTM Blade Back plate Table Guard front Guard back Guard holder Collection area

18. Food Residue Behind the Blade Hobart Berkel

19. Inoculation • Product inoculation and slicing • 1-cm strip on surface of product inoculated to contain L. monocytogenes at 108 CFU/cm2 • Held 1 hour at 5°C before slicing • Sampling method after each slice • 1-ply composite tissue method (Vorst et al. 2004. J. Food Prot. 67:2212-2217)

20. Kimwipe Method

21. Transfer of L. mono from Three Blades (~103 CFU/blade) to Different Slicer Locations after Slicing Ham at 4°C

22. Contamination of the Slicer During Operation • Other components of the slicer will be contaminated if a positive product is sliced on a commercial machine, not just the product being sliced

23. Outline 1. Transfer of L. monocytogenes to different components of a deli slicer 2. L. monocytogenes transfer to deli meats during slicing 3. Impact of biofilm formation and sublethal injury on Listeria transfer to deli meats 4. Development of a risk assessment for L. monocytogenes in deli meat

24. Contamination of Deli Meats During Slicing

25. Listeria Transfer Scenarios • Slicer blade to product • Product to slicer blade to product

26. Blade-Product Transfer • Slicer blade inoculated with a turkey slurry to contain ~103, 105, and 108Lm CFU/blade • Held 1 hour at 21 – 23°C before slicing • 3 replicates

27. L. monocytogenes Transfer from an Inoculated Slicer Blade (103 CFU/blade) to Turkey Breast, Salami and Bologna

28. Cumulative L. monocytogenes Transfer (%) from an Inoculated Slicer Blade (103 CFU/blade) to Turkey, Salami and Bologna

29. Extent of L. monocytogenes Transfer from a Slicer Blade to Turkey Breast, Bologna and Salami • 103 CFU/blade • Turkey: Slice 28 • Bologna: Slice 20 • Salami: Slice 23 • Except for salami, 99% of the original L. monocytogenes population is transferred in the first 10-15 slices, but much is unaccounted for.Assumption is that Listeria is spread into the immediate environment, remains on the blade or dies offWith salami continual transfer likely exceeds 30 slices

30. Product-Slicer-Product Transfer Products– turkey, salami, bologna • Surface inoculated to contain 105 and 108 CFU/cm2 • 1-cm strip on the product surface • Held 1 hour at 4.5°C before slicing Slicer inoculation • Inoculated product sliced 5 times to contaminate the blade at approximately 103 and 105 CFU/blade Product transfer • Uninoculated product sliced sequentially • 24 - 36 replicates

31. L. monocytogenes Transfer from Inoculated Turkey (IT) and Salami (IS) (105 CFU/cm2) to Uninoculated Product During Slicing

32. CumulativeL. monocytogenes Transfer (%) from Inoculated Turkey (IT) and Salami (IS) (105 CFU/cm2) to Uninoculated Product During Slicing

33. Extent of L. monocytogenes Transfer from Inoculated Turkey or Salami (105 CFU/cm2) to Uninoculated Product • Salami followed by salami • Slice 30 • Salami followed by turkey • Slice 10 • Turkey followed by salami • Slice 17

34. Transfer of L. mono from Three Inoculated Blades (~103 CFU/blade) to Ham Held for 5 Days at 4°C Before Sampling

35. Outline 1. Transfer of L. monocytogenes to different components of a deli slicer 2. L. monocytogenes transfer to deli meats during slicing 3. Impact of biofilm formation and sublethal injury on Listeria transfer to deli meats 4. Development of a risk assessment for L. monocytogenes in deli meat

36. Where Can Bacteria Hide?

37. Stages in biofilm formation

38. Biofilms on Slicer Blades? • Conditioning layer: meat, meat exudate • Unlikely to meet moisture requirement • will rely on RH of the operation and food products for moisture • Cleaning and friction from slicer will disrupt biofilms • Attached bacteria and food particles likely, but not biofilms

39. Persistence and Sublethal Injury • Persistent strains of L. monocytogenes attach to food contact surfaces and form biofilms more readily than non-persistent strains • Sublethal injury enhances resistance of Listeria to environmental stresses and leads to more persistent strains

40. Procedure • L. monocytogenes strains • Strong and weak biofilm formers • Healthy, starved, cold-stressed and chlorine-injured • Inoculate to contain ~108 CFU/blade • Allow to dry, incubate blades in humidity chamber at 78% RH, 22°C, 6 and 24 h • 24 replicates for healthy and cold-injured models each, and 36 replicates all others combinations

41. Transfer of Uninjured L. monocytogenes to Salami

42. Transfer of Chlorine-Injured L. monocytogenes to Turkey

43. Outline 1. Transfer of L. monocytogenes to different components of a deli slicer 2. L. monocytogenes transfer to deli meats during slicing 3. Impact of biofilm formation and sublethal injury on Listeria transfer to deli meats 4. Development of a risk assessment for L. monocytogenes in deli meat

44. Risk Assessment Framework Description of the Hazard (agent in the food) And adverse effects Hazard Identification What is the probability of consuming contaminated food AND what are the likely numbers of a pathogen in the food at the time of consumption Exposure Assessment A mathematical modelwhich predicts the probability of an adverse effect from a given dose. Hazard Characterization [Dose-Response] • Provides a RISK ESTIMATE • What is the nature and likelihood of the health risk? • Who and how many are likely to become ill? • What are the sources of variability and uncertainty in the information used? Risk Characterization Jaykus et al. 2007

45. Components of L. monocytogenes Transfer Model During Deli Meat Slicing Contamination Levels at retail (cfu/g) Prevalence • % frequency data Initial contamination level (log cfu/g) • Enumeration data • L. monocytogenes distribution in food • Lag time • Growth rate • Storage time • Refrigeration temperature • Maximum growth Growth in the retail refrigerator • L. monocytogenes transfer rate • product composition • type of slicer blade Cross contamination during deli slicing Growth in the home refrigerator Left-over portions Contamination level at consumption (log CFU)/g) • Serving size Contamination level per serving Jaykus et al. 2007

46. Overall Conclusions • Slicing a contaminated product will lead to contamination of all slicer components • > 90% of Listeria transfer from the blade to the product occurs during the first 10-15 slices of delicatessen meats after mechanical or knife slicing • Deli meats will “clean” the slicer blade, but with varying effectiveness

47. Overall Conclusions Additional Factors Impacting Listeria Transfer • Product composition • Moisture, Fat • Product temperature • Order in which products are sliced • Model and design of the slicer • Characteristics of L. monocytogenes • Healthy vs. injured • Strong or weak biofilm former

48. Take Home Message • Avoid the first 10 slices? • Do opened packages of non-recalled product pose a significant risk?

49. MSU Listeria Slicer Team • Dr. Keith L. Vorst • Dr. Lindsey Keskinen • Dr. Zhinong Yan • Dr. Bradley P. Marks • Dr. Ewen Todd • Dr. Gary Burgess • Amanda Benoit • Funding • FDA • USDA-NAFSS • USAD-NISFI

50. Referencec : www.slideshare.com