Using risk assessment to design
effective intervention - Case study:
Listeria and deli meat
Martin Wiedmann
Department of Food Science
Cornell University, Ithaca, NY
E-mail: [email protected]
Phone: 607-254-2838
Acknowledgements
• Funding sources: • USDA Food Safety and Inspection Service Contract # AG-3A-
C-09-0028 • USDA-NIFA Specials Research Grants
• Staff and students • S. Roof, C. Simmons, E. Wright, S. Warchocki, K. Hoelzer, B.
Sauders, M. Stasiewicz • Collaborators:
• New York state Department of Health; USDA-FSIS • Purdue University (Haley Oliver and Susan R. Hammons);
North Carolina Ag &Tech (Salam A. Ibrahim) • Retailers
Outline
• Listeria monocytogenes and deli meats – the issue
• The risk assessments addressing the issue – Interagency Risk Assessment – Listeria
monocytogenes in Retail Delicatessens Technical Report (slides provided by Janell Kause, USDA FSIS)
• The path forward: interventions • Conclusions and Lessons learned
Listeria monocytogenes
• Gram-positive animal and human food-borne pathogen • Facultative intracellular pathogen • Causes abortion, meningitis, and septicemia • Can grow at low temperatures • High infectious dose
• Causes an estimated 1,600 illness and 255 deaths/year in US • Equivalent to about 5 cases/million population • L. monocytogenes ranks #3 in number of deaths
due to foodborne disease per year in the US
FDA-FSIS Risk Assessment for L. monocytogenes in Ready-to-Eat Foods (2003)
Sample Source
*
VISIT 2
VISIT 3
VISIT 1
*
* *
*
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* *
* * *
*
*
* *
Sample Ribotype Sample Source RiboPrint® Pattern
1039C (E) Floor drain, raw materials area
1039C (E) Floor drain, hallway to finished area
1039C (IP) Troll Red King Salmon, in brine, head area
1039C (IP) Troll Red King Salmon, in brine, belly area
1039C (IP) Brine, Troll Red King Salmon
1039C (IP) Faroe Island Salmon, in brine, head area
1039C (F) Smoked Sable
1039C (F) Cold-Smoked Norwegian Salmon
1044A (E) Floor drain, brining cold room 1
1044A (R) Raw Troll Red King Salmon, head area
1044A (IP) Brine, Faroe Island Salmon
1045 (R) Raw Troll Red King Salmon, belly area
1045 (IP) Faroe Island Salmon, in brine, head area
1053 (IP) Norwegian Salmon, in brine
1062 (E) Floor drain #1, raw materials preparation
1039C (E) Floor drain #1, raw materials preparation
1039C (E) Floor drain, brining cold room 1
1039C (E) Floor drain #2, raw materials preparation
1039C (E) Floor drain #2, raw materials receiving
1039C (E) Floor drain, finished product area
1039C (E) Floor drain, hallway to finished area
1039C (IP) Brine, Troll Red King Salmon
1039C (F) Smoked Sable
1044A (IP) Sable, in brine
1044A (IP) Brine, Faroe Island Salmon
1062 (IP) Brine, Norwegian Salmon
7
L. monocytogenes persisted in rubber floor mats despite sanitation
Listeria can be protected from sanitizer in “micro-cracks”, but can
be squeezed out by pressure if people stand on mats
2000 US outbreak - Environmental persistence of L. monocytogenes?
• 1988: one human listeriosis case linked to hot dogs produced by plant X
• 2000: 29 human listeriosis cases linked to sliced turkey meats from plant X
From 2013 Interagency Risk Assessment: L. monocytogenes in Retail Delicatessens
Retrospective study provided evidence for L. monocytogenes
persistence in 16/50 retail establishments
Cross-sectional study provided data on L. monocytogenes prevalence
in different sites at retail (prospective study of 121 stores)
L. monocytogenes at Retail – Data from 241 Retail Deli Establishments in
New York State (2005 – 2007)
Phase Positive food
samples
Positive
environmental
samples
Stores with at
least one
positive sample
1. Large chain stores
(n=121)
2.7%
(5/183 samples)
13.0%
(151/1,161 samples)
60.3%
(73/121 stores)
2. Small stores
(n=60)
0.6 %
(1/157 samples)
12.9 %
(85/661 samples)
55.0%
(33/60 stores)
3. Stores with a history
of poor inspection
scores (n=60)
0.8%
(1/122 samples)
13.2%
(95/718 samples)
65.0 %
(39/60 stores) 12
Contamination originating at retail was estimated to account for 63 to 84%
of listeriosis cases due to selected RTE deli meats
Of those illnesses and deaths from L. monocytogenes from deli meat
consumption, approximately 83% are attributed to deli meat sliced and
packaged at retail facilities. 13
L. monocytogenes in retail
• 30 retail deli operations sampled monthly over 6 months
• Among 4, 512 samples 9.4% (424) were positive for L. monocytogenes
– 72/1604 (4.5%) of “Food Contact Surface” samples
– 18/540 (3.3%) of “Transfer Point” samples
– 334/2368 (14.1%) of “Non-Food Contact Surface” samples
L. monocytogenes Positive Samples by Site
Food Contact Non-Food Contact
Site + Total % Site + Total %
Slicer Blade 5 180 2.8 3-Basin Sink Ext 6 180 3.3
Deli Case 4 179 2.2 Floor-Wall Junct (3) 24 180 13.3
Case by Meat 2 33 6.1 1-Basin Sink Exterior 7 164 4.3
Deli Case Tray 4 180 2.2 Floor Wall Junct (1) 31 111 27.9
3-Basin Sink Intr* 14 179 7.8 Deli Drain 36 180 20.0
1-Basin Sink Intr* 30 164 18.3 Floor Adj to Drain 46 180 25.6
Cold Room Rack 4 180 2.2 Deli Floor 23 179 12.8
Cutting Board 3 152 2.0 Cold Room Floor 36 179 20.1
Rewrap table 1 179 0.6 Cold Room Wall 4 180 2.2
Counter 5 178 2.8 Cold Room Drain 40 119 33.6
Transfer Point Standing Water 16 90 17.8
Site + Total % Squeegee 36 132 27.3
Slicer Knob 3 180 1.7 Cart Wheel 14 180 7.8
Case Handle 8 180 4.4 Hose 6 134 4.5
Scale Top 7 180 3.9 Trash Can 9 180 5.0
*1- and 3 basin sink interiors are not considered food contact surfaces by FDA and USDA-FSIS
Presence of L. monocytogenes in Different Environments
• Natural environments: 1.4% (n=898)
• Urban environments: 7.4% (n=907)
• Ruminant farms – Bovine farms with listeriosis cases: 24.3% (n=616)
– Bovine farms without listeriosis cases: 20.1% (n=643)
– Small ruminant farms with listeriosis: 32.9% (n=322)
– Small ruminant farms without listeriosis: 5.9% (n=475)
Sauders et al., 2013, AEM; Nightingale et al. 2004, AEM
Store Month 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
FOOD CONTACT
07 0/9 0/8 1/9 0/9 0/9 0/7 2/9 0/9 0/8 1/8 0/9 0/6 0/9 0/9 0/9
08 0/9 5/9 0/9 0/8 0/9 0/7 0/9 0/9 0/8 3/8 0/9 0/10 0/9 0/9 0/9
09 0/9 0/9 0/9 0/9 0/9 0/9 0/10 0/9 0/8 1/9 0/9 0/9 1/9 0/9 0/9
10 0/9 0/9 0/9 0/9 0/9 0/7 0/9 1/9 0/8 1/8 0/9 0/9 0/9 0/9 0/9
11 0/9 0/10 0/9 0/10 0/9 0/10 1/9 1/9 0/8 1/9 0/9 1/9 2/9 0/9 0/9
12 0/9 1/9 0/9 1/8 0/9 0/7 0/9 0/9 0/8 1/8 1/9 0/9 0/9 0/9 0/9
TRANSFER POINT
07 0/3 1/3 0/3 0/3 0/3 0/3 0/3 0/3 0/3 0/3 0/3 0/3 0/3 0/3 0/3
08 0/3 2/3 0/3 0/3 0/3 0/3 0/3 0/3 0/3 1/3 0/3 0/3 0/3 0/3 0/3
09 0/3 0/3 0/3 0/3 0/3 0/3 0/3 0/3 0/3 0/3 0/3 0/3 0/3 0/3 0/3
10 0/3 1/3 0/3 0/3 0/3 0/3 0/3 0/3 0/3 0/3 0/3 0/3 0/3 0/3 0/3
11 0/3 0/3 0/3 0/3 0/3 0/3 0/3 0/3 0/3 0/3 0/3 2/3 0/3 0/3 0/3
12 0/3 0/3 0/3 0/3 0/3 0/3 0/3 0/3 0/3 0/3 0/3 0/3 0/3 0/3 0/3
NON-FOOD CONTACT
07 0/11 4/14 0/14 0/14 0/14 0/12 10/14 5/14 0/10 7/14 0/15 0/11 0/14 0/12 0/12
08 0/11 6/14 0/16 0/14 0/14 0/12 8/14 4/14 0/10 8/13 0/14 0/10 0/14 0/11 0/12
09 0/11 6/14 0/14 0/14 0/14 0/14 1/15 1/14 0/10 7/14 0/14 0/11 0/14 0/12 0/13
10 0/13 5/15 0/14 2/14 0/14 0/12 7/14 0/14 0/11 3/14 0/14 0/11 2/14 0/10 0/12
11 1/11 5/14 0/14 1/14 0/14 0/14 8/14 1/14 1/11 2/14 0/14 2/11 1/14 1/11 0/12
12 0/11 8/15 0/14 1/14 0/14 0/12 8/14 0/14 0/11 3/14 1/14 0/11 2/14 0/11 0/12
L. monocytogenes Positive Samples: Stores 1–15 by Month
14/30 retail delis showed evidence for L. monocytogenes persistence
April May June July August September October November December
Food Contact Sites
Sl icer - - - - - - - - -
Deli case NT NT NT - - - - - -
Deli case near raw meat NT NT NT - - - - - -
Deli case trays NT NT NT - - - - - -
3-basin sink interior NT NT NT CU-57,267 - - - - -
1-basin sink interior NT NT NT CU-258,69 - - - CU-294,321 -
Cold room rack - - - - - - - - -
Cutting board NT NT NT NT - - NT NT -
Rewrap table NT NT NT - - - - - -
Counter NT NT NT - - - - - -
Non-food contact sites
3-basin sink exterior NT NT NT - - - - - -
Floor/wall junction (3-basin) CU-258,69 CU-258,69 CU-258,69 CU-258,69 CU-258,69 CU-8,96 - - CU-258,69
1-basin sink exterior NT NT NT CU-258,69 - - CU-258,69 - CU-258,69
Floor/wall junction (1-basin) NT NT NT CU-258,69 - - CU-258,69 CU-258,69 CU-258,69
Deli drain NT NT NT CU-258,69 CU-258,333 - - CU-258,69 CU-258,69
Floor adjacent to drain - CU-258,69 CU-258,69 CU-258,69 CU-258,69 - CU-258,69 CU-258,69 CU-258,69
Deli floor NT NT NT CU-258,69 - - - CU-258,69 -
Cold room floor NT NT NT CU-258,69 CU-295,329 - CU-258,69 CU-258,69 CU-258,69
Cold room wall CU-258,69 - - - - - - - -
Cold room drain NT NT NT CU-258,69 CU-258,69 - CU-258,69 CU-258,69 CU-258,69
Standing water NT NT NT NT - - NT NT -
Squeegee NT NT NT CU-258,69 CU-258,69 - CU-258,69 CU-258,69 CU-258,69
Cart Wheel - - CU-258,69 CU-258,69 - - - - -
Hose NT NT NT - CU-258,69 - - - -
Trash can - - CU-258,69 - CU-258,69 - - - -
Transfer Points
Slicer knob - - - - - - - - -
Case handle - - - - - - - - -
Scale NT NT NT - - - - - -
19
20
Effects of sanitation related scenarios on Predicted Risk of Invasive Listeriosis for the
Susceptible Population
Scenario Multiple
Niche
100W
No
Niche
Incoming
Growth
Chub
Incoming
Non-growth
Chub
Temp.
Control
Niche &
Temp.
Control
Wash & Sanitize: Increase the
effectiveness of cleaning from simply
washing to washing and sanitizing.
-1.6 1.7 -0.6 2.0 -1.3 -7.6*
Clean 8 Sporadic: Double the number
of sites cleaned from 4 to 8.
-4.2 -4.1* -0.7 -1.9 -0.5 1.3
No Sanitation: No wiping, washing, or
sanitizing.
41.3* 7.9* 2.9* 23.5* 11.9* 50.2*
No Sporadic Cleaning: Clean as
required by the 2009 FDA Food Code,
but no additional sporadic cleanings.
3.0 -3.0 -0.4 1.7 1.7 3.5
NFCS As FCS: Workers clean deli
NFCSs at same rate as FCS.
-3.0 0.7 -0.6 0.3 -5.4* 0.9
Scenario Multiple
Niche
100W
No Niche Incoming
Growth Chub
Incoming Non-
growth Chub
Temp.
Control
Niche & Temp.
Control
No Glove: Workers do not use
gloves when serving customers.
5.1* 2.5 1.2 8.5* 6.0* 7.0*
No Contact Glove Case: Workers
do not use their hands to open
the deli case (e.g. if a floor
switch is used).
-1.4 -3.4 -1.3 1.3 1.3 -0.3
Pre-slice: Workers pre-slice RTE
products in the morning, after
cleaning
6.0* 24.9* 49.5* -34.4* 19.2* 1.0
Separate Slicer: Workers use a
separate slicer for RTE products
that support growth of L.
monocytogenes.
-6.3* -0.6 -1.7* 22.7* -0.8 4.6
Effects of selected worker behavior related scenarios on Predicted Risk of Invasive Listeriosis
for the Susceptible Population
Scenario Multiple
Niche 100W
No Niche Incoming
Growth
Chub
Incoming Non-
growth Chub
Temp.
Control
Niche & Temp.
Control
All GI: Reformulate all RTE
products sold at the retail deli
that would otherwise support
L. monocytogenes growth to
include growth inhibitors.
-96.0* -95.2* -97.5* -94.5* -94.4* -94.8*
No GI: Reformulate all RTE
products that support L.
monocytogenes growth that
are sold at the retail deli to
not include GI to restrict L.
monocytogenes growth.
184.1* 191.5* 35.1* 190.5* 187.7* 188.9
Effects of growth inhibitor related scenarios on Predicted Risk of Invasive Listeriosis for the
Susceptible Population
Effects of selected cross contamination related scenarios on Predicted Risk of Invasive Listeriosis
for the Susceptible Population
Scenario Multiple
Niche 100W
No Niche Incoming
Growth Chub
Incoming
Non-growth
Chub
Temp.
Control
Niche & Temp.
Control
Transfers to 0: Cross
contamination results only
from the deli slicer.
-4.3 2.5 1.0 3.7 0.2 -0.3
Transfers and Slicer to 0: No
cross contamination in the
retail deli.
-33.8* -18.6* -9.5* -60.8* -19.2* -30.4*
Reduce Level: Mean incoming
L. monocytogenes log10
concentration in all RTE
products lowered from -9.2 to
-9.5 log10 cfu/g.
-21.6* -24.2* -1.1 -9.8* -22.5* -15.6*
Effects of selected storage time and temperature related scenarios on Predicted Risk of Invasive
Listeriosis for the Susceptible Population
Scenario Multiple
Niche 100W
No Niche Incoming
Growth
Chub
Incoming
Non-growth
Chub
Temp.
Control
Niche & Temp.
Control
Temp = 5°C: Set the retail
deli case temperature to
5°C (41°F)
-4.8 -14.3* -8.1* -2.8 NA NA
No Growth (T=-5°C): At this
temperature, no L.
monocytogenes growth will
occur.
-16.5* -21.3* -18.2* -5.7* NA NA
Shorten Time in Retail
Delis: Reduce the length of
time RTE products are held
before they are sold or
disposed from 7 to 4 days.
-2.5 3.3 -1.2 2.0 -0.2 1.7
Interventions to control L. monocytogenes at retail
• Control growth in deli meats through reformulation – Based on various models, this is by far the most effective
intervention
• Control cross contamination – Multiple contributing factors (employee behavior, niches) – No simple solutions
• Control contamination on incoming products • Continued focus on sanitation • Focus on key routes of contamination and cross
contamination (e.g., slicers)
Summary and conclusions
• L. monocytogenes contamination is a challenge across the food chain, not just in processing facilities – Common presence of L. monocytogenes in many environments
presents a considerable challenge • Risk assessments and growth modelling data suggest the
reformulation of RTE deli meats represents the most effective intervention
• Do not trust risk assessments too much: – Many aspects of the complexity of food systems are difficult to
model – We model what we can wrap our head around and what we
have data for • Over-reliance on insights based on outbreaks can be dangerous