Dr. Elliot Ryser Department of Food Science and Human Nutrition Michigan State University East Lansing, MI September 14, 2011

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

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.

USDA Listeria Alternatives Implemented October 2003

Deli Meat Recalls, Year Number of recalls Ham Turkey Chicken Beef Corned Beef Other > 84 recalls > 53 million lbs

YearNumber of Recalls Recalled Product (lbs) , , , ,500 10

 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

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

 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

Distribution of Listeria spp. in a Local Deli/Restaurant Location ListeriaL. seeligeriL. innocuaL. mono Basement Kitchen Front line 7700 Sandwich line Seafood case 5050 Cheese case 9450 Meat case 7430 Display floor Open back case 1100 Board (meat, cheese) Slicer (Hobart, sandwich line) 8701 Slicer (Bizerba, deli) 5401 Slicer (Bizerba, cheese) 2200 Slicer ( Hobart, basement sandwich line )0000 Slicer (Hobart), basement, cheese Total

_________________________________________________ LocationListeria pos/# of positive visits # tested (%)ListeriaLM _______________________________________________________ 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, cheese42/154 (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) _________________________________________________________________

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

Back plate Table Guard front Guard back Collection area Blade Guard holder

HobartBerkel Food Residue Behind the Blade

 Product inoculation and slicing  1-cm strip on surface of product inoculated to contain L. monocytogenes at 10 8 CFU/cm 2  Held 1 hour at 5°C before slicing  Sampling method after each slice  1-ply composite tissue method (Vorst et al J. Food Prot. 67: )

 Other components of the slicer will be contaminated if a positive product is sliced on a commercial machine, not just the product being sliced

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

Slicer blade to product Product to slicer blade to product

 Slicer blade inoculated with a turkey slurry to contain ~10 3, 10 5, and 10 8 Lm CFU/blade  Held 1 hour at 21 – 23°C before slicing  3 replicates

 10 3 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 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

Products– turkey, salami, bologna  Surface inoculated to contain 10 5 and 10 8 CFU/cm 2  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 10 3 and 10 5 CFU/blade Product transfer  Uninoculated product sliced sequentially  replicates

 Salami followed by salami  Slice 30  Salami followed by turkey  Slice 10  Turkey followed by salami  Slice 17

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

 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

 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

 L. monocytogenes strains  Strong and weak biofilm formers  Healthy, starved, cold-stressed and chlorine-injured  Inoculate to contain ~10 8 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

Transfer of Uninjured L. monocytogenes to Salami

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

Risk Assessment Framework Hazard Identification Exposure Assessment Hazard Characterization [Dose-Response] Risk Characterization Description of the Hazard (agent in the food) And adverse effects 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 A mathematical model which predicts the probability of an adverse effect from a given dose. 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? Jaykus et al. 2007

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

 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 slices of delicatessen meats after mechanical or knife slicing  Deli meats will “clean” the slicer blade, but with varying effectiveness

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

 Avoid the first 10 slices?  Do opened packages of non-recalled product pose a significant risk?

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

 Referencec : 50