Longitudinal Study of Listeria monocytogenes Prevalence and Persistence in Retail Delis

Haley F. Oliver, PhDPurdue University

1

Interagency Risk Assessment - L. monocytogenes in Retail Delicatessens Public Meeting

Washington, DC - May 22nd, 2013

Four-Phase Longitudinal StudyHypotheses

• L. monocytogenes persists on food and non-food contact surfaces in retail delis

• Cross-contamination occurs between non-food contact surfaces and food contact surfaces

2May 22nd, 2013Interagency Risk Assessment--Listeria monocytogenes in Retail Delicatessens Public Meeting

Four Phase Longitudinal Study - Overview

• Phase 1: Monthly sampling (prior to operation) for LM and Listeria species in 15 stores (5 stores/state) for 3 months

– Also included APC and ATP testing

• Phase 2: Monthly sampling (during operation) for LM and Listeria species in 30 stores (10 stores/state) for 6 months

• Phase 3: Develop interventions to be implemented in stores (based on phase 1 and 2 results)

• Phase 4: Repeat phase 2 with interventions in place

Initiated under FSIS/Office of Public Health Science

3May 22nd, 2013Interagency Risk Assessment--Listeria monocytogenes in Retail Delicatessens Public Meeting

Results of pre-op sampling (Phase 1)

• 21/315 samples positive for L. monocytogenes (6.7%)– 2/315 samples positive for non-LM Listeria spp. (0.63%)

• Quantification data indicate that drains and floors can have >104 L. monocytogenes/sponge

LM pos. Other List. Species pos.

Trash cans 1/45 (2.2%) 1/45 (2.2%)

Carts 2/45 (4.5%) 0

Pans 1/45 (2.2%) 0

Floor next to drain 7/45 (15.5%) 0

Wall/floor juncture 8/45 (17.7%) 0

Walk-in cooler & shelving 2/45 (4.5%) 0

Slicer casing 0 1/45 (2.2%) 4

Phase 1 Pre-Op LM+ by Store - Evidence of L. monocytogenes Persistence

5

April May June

Trash can - 7

Cart - 4 7Pan 10 - -Floor Next to Drain

2, 7, 13 2, 7 2, 7

Wall/Floor Juncture

2, 5, 7 2, 7 2, 7, 10

Walk-in Cooler & Shelving

5, 11 - -

Slicer Casing - - -May 22nd, 2013Interagency Risk Assessment--Listeria monocytogenes in Retail Delicatessens Public Meeting

Results – Longitudinal Testing (Phase 2)

• 30 stores

• Total samples = 4512

• 9.4% (425/4512) positive for LM

– 73/1604 (4.5%) of “Food Contact Surfaces” positive for LM

– 18/540 (3.3%) of “Transfer Points” positive for LM

– 334/2368 (14.1%) of “Non-Food Contact Surfaces” positive for LM

6May 22nd, 2013Interagency Risk Assessment--Listeria monocytogenes in Retail Delicatessens Public Meeting

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 2.2Floor-Wall Junct. (under 3-basin sink) 24/180 13.3

Case by Meat 2/33 6.1 1-Basin Sink Exterior 7/164 4.3

Deli Case Tray 4/180 2.2Floor/Wall Junct (under 1-basin sink) 31/111 27.9

3-Basin Sink Interior 14/179 7.8 Deli Drain 36/180 20.0

1-Basin Sink Interior 30/164 18.3Floor Adjacent to Deli Drain 46/180 25.6

Cold Room Rack 4/180 2.2 Deli Floor 23/179 12.8Cutting Board 4/152 2.6 Cold Room Floor 36/179 20.1Rewrap table 1/179 0.6 Cold Room Wall 4/180 2.2Counter 5/178 2.8 Cold Room Drain 40/119 33.6

Transfer Point Standing Water 16/90 17.8Site Total % Squeegee 36/132 27.3

Slicer Knob 3/180 1.7 Cart Wheel 14/180 7.8Case Handle 8/180 4.4 Hose 6/134 4.4Scale Top 7/180 3.9 Trash Can 9/180 5.0

7May 22nd, 2013Interagency Risk Assessment--Listeria monocytogenes in Retail Delicatessens Public Meeting

StoreMonth 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 0/908 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 0/909 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 0/910 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 0/911 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 0/912 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 0/308 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 0/309 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 0/310 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 0/311 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 0/312 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 0/1208 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 0/1209 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 0/1310 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 0/1211 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 0/1212 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

8May 22nd, 2013Interagency Risk Assessment--Listeria monocytogenes in Retail Delicatessens Public Meeting

Stores 16-30 by MonthStore

Month 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

FOOD CONTACT

08 1/10 0/9 1/9 0/9 0/9 1/8 5/9 1/10 2/8 0/9 0/9 5/9 0/9 1/9 0/9

09 0/9 0/9 0/9 1/9 0/9 0/8 0/9 3/10 0/8 0/9 0/9 0/9 0/9 1/9 0/9

10 1/10 0/9 1/9 0/9 0/9 1/10 1/9 1/10 0/9 0/9 0/9 0/9 0/10 0/9 0/9

11 1/10 1/9 0/9 0/9 0/9 2/9 0/9 1/10 1/8 0/10 0/9 0/9 0/8 1/9 0/9

12 3/10 0/9 0/9 1/9 0/9 0/10 0/9 0/10 0/8 0/9 0/9 0/9 0/9 1/9 0/9

01 1/9 0/9 1/9 1/9 1/9 0/8 0/9 1/9 0/8 0/9 0/9 0/9 1/8 1/9 0/9

TRANSFER POINT

08 0/3 0/3 0/3 0/3 0/3 0/3 3/3 0/3 0/3 0/3 0/3 2/3 0/3 0/3 0/3

09 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 0/3 0/3

10 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

11 0/3 1/3 0/3 0/3 0/3 1/3 0/3 0/3 0/3 0/3 0/3 0/3 1/3 0/3 0/3

12 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 0/3

01 0/3 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 0/3

NON-FOOD CONTACT

08 4/14 0/12 0/14 0/11 0/14 5/14 5/12 9/15 4/12 1/12 0/14 4/11 9/15 3/14 0/14

09 2/14 0/12 0/14 0/11 0/14 5/14 0/11 8/14 6/11 0/13 0/14 0/12 9/14 1/14 0/14

10 1/14 0/13 0/14 1/11 0/14 3/13 0/11 7/15 8/13 0/13 1/14 0/12 9/14 2/14 0/14

11 3/15 3/12 0/14 0/12 1/15 2/14 0/12 5/14 10/13 0/15 2/14 0/12 9/15 0/14 0/14

12 4/15 0/12 0/14 0/11 0/14 4/14 0/12 4/15 7/13 0/11 1/14 0/11 8/15 0/14 0/14

01 0/14 0/13 2/14 0/11 0/14 4/14 0/12 9/15 6/12 0/11 0/14 0/11 9/15 2/14 0/149May 22nd, 2013Interagency Risk Assessment--Listeria monocytogenes in Retail Delicatessens Public Meeting

30 retail stores – subtyping conclusions

10

• 12/30 stores show low LM prevalence (≤4 positive samples; <2% prevalence)

• 4/30 stores show low LM prevalence with a single high prevalence contamination event

• 14/30 stores show evidence for persistence (preliminary sub-classification)• 9 stores show clear evidence for persistence on “non-

FCS” area with occasional FCS contamination with persistent type

• 2 stores show clear evidence for persistence on non FCS area; persistent strain not isolated from FCS

• 3 stores show possible short term persistence (same subtype isolated in 2 or 3 different months with ≤ 8 total positive samples), two on FCS, one on non-FCS.

May 22nd, 2013Interagency Risk Assessment--Listeria monocytogenes in Retail Delicatessens Public Meeting

Low LM prevalence with a sporadic high prevalence event           

August  September October November December JanuaryFood Contact Sites            Slicer  CU-258,69 - - - - -Deli case - - - - - -Deli case near raw meat NT NT NT NT NT NTDeli case trays CU-258,69 - - - - -3-basin sink interior - - - - - -1-basin sink interior CU-258,69 - - - - -Cold room rack - - - - - -Cutting board - - - - - -Rewrap table CU-258,69 - - - - -Counter CU-258,69 - - - - -Non-food contact sites   - - -    3-basin sink exterior CU-258,333 - - - - -Floor/wall junction (3-basin) - - - - - -1-basin sink exterior CU-258,69 - - - - -Floor/wall junction (1-basin) NT NT NT NT NT -Deli drain - - - - - -Floor adjacent to drain CU-258,69 - - - - -Deli floor - - - - - -Cold room floor - - - - - -Cold room wall - - - - - -Cold room drain CU-258,69 - - - - -Standing water NT NT NT NT NT NTSqueegee NT NT NT NT NT NTCart Wheel - - - - - -Hose - NT - - NT NTTrash can - - - - - -Transfer Points   - - -    Slicer knob - - - - - -Case handle CU-258,69 - - - - -Scale  CU-258,69 - - - - - 11

PFGE data - low prevalence with a high prevalence event (11 entries)

PFGE-ApaI

20.00

30.00

40.00

60.00

80.00

100.0

012

0.00

140.0

016

0.00

180.0

020

0.00

250.0

028

0.00

350.0

0

400.0

045

0.00

500.0

055

0.00

700.0

020

00 5.0

0E3

2.00E

4 5.0

0E4

PFGE-AscI

20.00

30.00

40.00

60.00

80.00

100.0

0

120.0

014

0.00

160.0

018

0.00

200.0

022

0.00

240.0

0

300.0

0

350.0

0

400.0

045

0.00

500.0

055

0.00

700.0

020

00 5.0

0E3

2.00E

4 5.0

0E4 Key

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Site #

1

5

10

27

28

8

11

14

18

6

25

Store #

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LineageCU Pattern Number

CU-258,69

CU-258,69

CU-258,69

CU-258,69

CU-258,69

CU-258,333

CU-258,69

CU-258,69

CU-258,69

CU-258,69

CU-258,69

Sampling date

.

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Allelic typeCU Pattern No_Asc1

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CU Pattern No_Apa1

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FCS/ NFCSSite Subtype

Slicer CU-258,69

Deli case trays CU-258,69

1-basin sink interior CU-258,69

Rewrap table CU-258,69

Counter CU-258,69

3-basin sink exterior

CU-258,333

1-basin sink exterior

CU-258,69

Floor adjacent to drain

CU-258,69

Cold room drain CU-258,69

Case handle CU-258,69

Scale CU-258,69

12May 22nd, 2013Interagency Risk Assessment--Listeria monocytogenes in Retail Delicatessens Public Meeting

30 retail stores – subtyping conclusions

13

• 12/30 stores show low LM prevalence (≤4 positive samples; <2% prevalence)

• 4/30 stores show low LM prevalence with a single high prevalence contamination event

• 14/30 stores show evidence for persistence (preliminary sub-classification)• 9 stores show clear evidence for persistence on “non-

FCS” area with occasional FCS contamination with persistent type

• 2 stores show clear evidence for persistence on non FCS area; persistent strain not isolated from FCS

• 3 stores show possible short term persistence (same subtype isolated in 2 or 3 different months with ≤ 8 total positive samples), two on FCS, one on non-FCS.

May 22nd, 2013Interagency Risk Assessment--Listeria monocytogenes in Retail Delicatessens Public Meeting

LM Persistence on non-food contact surfaces with sporadic FCS positive                 

April May  June  July August  September October November DecemberFood Contact Sites                  Slicer  - - - - - - - - -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-258,691-basin sink exterior NT NT NT CU-258,69 - - CU-258,69 - CU-258,69Floor/wall junction (1-basin) NT NT NT CU-258,69 - - CU-258,69 CU-258,69 CU-258,69Deli drain NT NT NT CU-258,69 CU-258,333 - - CU-258,69 CU-258,69Floor adjacent to drain - CU-258,69 CU-258,69 CU-258,69 CU-258,69 - CU-258,69 CU-258,69 CU-258,69Deli 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-258,69Cold room wall CU-258,69 - - - - - - - -Cold room drain NT NT NT CU-258,69 CU-258,69 - CU-258,69 CU-258,69 CU-258,69Standing water NT NT NT NT - - NT NT -Squeegee NT NT NT CU-258,69 CU-258,69 - CU-258,69 CU-258,69 CU-258,69Cart 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 - - - - - -

14May 22nd, 2013Interagency Risk Assessment--Listeria monocytogenes in Retail Delicatessens Public Meeting

LM Persistence on non-food contact surfaces with same type found multiple times on FCS

                  April May  June  July August  September October November DecemberFood Contact Sites                  Slicer  - - - - CU-258,323 - - - -Deli case NT NT NT - - - - - -Deli case near raw meat NT NT NT NT NT - NT - NTDeli case trays NT NT NT - - - - - -3-basin sink interior NT NT NT - - - - - -1-basin sink interior NT NT NT CU-294,321 CU-294,321 CU-57,267 CU-57,267 CU-57,267 LMCold room rack - - - - - - - - -Cutting board NT NT NT NT NT NT NT NT NTRewrap table NT NT NT - - - - - -Counter NT NT NT - CU-11,320 - - - -Non-food contact sites                  3-basin sink exterior NT NT NT - - - - - -Floor/wall junction (3-basin) - - CU-11,320 - CU-11,320 - - - -1-basin sink exterior NT NT NT - - - - - -Floor/wall junction (1-basin) NT NT NT - - - - - -Deli drain NT NT NT CU-11,320 CU-11,320 CU-11,320 CU-40,96 - LMFloor adjacent to drain - - - CU-11,320 CU-11,320 CU-11,320 CU-11,320 - LMDeli floor NT NT NT CU-11,320 CU-11,320 CU-11,320 - - -Cold room floor NT NT NT CU-11,320 CU-11,320 CU-11,320 - - -Cold room wall - - - CU-11,320 CU-11,320 - - - -Cold room drain NT NT NT CU-11,320 CU-11,320 CU-8,96 CU-11,320 CU-57,267 LMStanding water NT NT NT NT NT NT NT NT NTSqueegee NT NT NT CU-11,320 - CU-11,320 - - -Cart Wheel - - - - CU-11,320 CU-11,320 - - -Hose NT NT NT - - - - - -Trash can - - - - - - - CU-11,320 -Transfer Points                  Slicer knob NT NT NT - CU-258,323 - - - -Case handle NT NT NT - - - - - -Scale  NT NT NT - - - - - -

15May 22nd, 2013Interagency Risk Assessment--Listeria monocytogenes in Retail Delicatessens Public Meeting

Persistence on non-FCS only                 

April May  June  July August  September October November DecemberFood Contact Sites                  Slicer  - - - - - - - - -Deli case NT NT NT - - - - - -Deli case near raw meat NT NT NT NT NT NT NT NT NTDeli case trays NT NT NT - - - - - -3-basin sink interior NT NT NT - - - - - -1-basin sink interior NT NT NT - - - CU-40,96 CU-200,227 -Cold room rack - - - - - - - - -Cutting board 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-11,326 - - - - - - - -1-basin sink exterior NT NT NT - - - - - -Floor/wall junction (1-basin) NT NT NT CU-8,340 CU-8,340 CU-8,340 - CU-8,340 -Deli drain NT NT NT - CU-8,326 - - - -Floor adjacent to drain CU-8,340 - - - CU-11,326 - - - -Deli floor NT NT NT CU-8,340 - - - - -Cold room floor NT NT NT CU-8,340 - - - - -Cold room wall - - - - - - - - -Cold room drain NT NT NT NT NT NT NT NT NTStanding water NT NT NT CU-8,340 CU-8,340 - - - -Squeegee NT NT NT - - - - - -Cart Wheel - - - CU-8,340 - - - - -Hose NT NT NT - - - - - -Trash can - - - - - - - - -Transfer Points                  Slicer knob NT NT NT - - - - - -Case handle NT NT NT - - - - - -Scale  NT NT NT - - - - - - 16

May 22nd, 2013Interagency Risk Assessment--Listeria monocytogenes in Retail Delicatessens Public Meeting

            August  September October November December JanuaryFood Contact Sites            Slicer  - - - - - -Deli case - - - - - -Deli case near raw meat NT NT NT NT - NTDeli case trays - - - CU-262,79 - -3-basin sink interior CU-294,321 - CU-294,321 - - -1-basin sink interior - - - CU-262,79 - -Cold room rack - - - - - -Cutting board NT NT - - - NTRewrap table - - - - - -Counter - - - - - -Non-food contact sites            3-basin sink exterior - - - CU-262,79 - -Floor/wall junction (3-basin) - CU-11,320 - - - -1-basin sink exterior - - - - - -Floor/wall junction (1-basin) CU-294,321 CU-11,320 - NT - CU-11,320Deli drain - CU-11,320 - -   -Floor adjacent to drain - CU-263,319 - - CU-263,318 CU-11,320Deli floor CU-11,320 - - - CU-11,320 -Cold room floor CU-11,320 - CU-11,320 CU-263,319 - CU-11,320Cold room wall - - - - - -Cold room drain CU-11,320 CU-11,320 CU-11,320 - NT -Standing water NT NT NT NT CU-11,320 NTSqueegee - - CU-11,320 - CU-11,320 CU-11,320Cart Wheel - - - - - -Hose - - NT - - -Trash can CU-11,320 - - - - -Transfer Points            Slicer knob - - - - - -Case handle - - - CU-262,79 - -Scale  - - - - - -

Persistence on non-FCS & possible short term persistence of 2nd subtype on FCS

17

Quantitative data

18

Occasional high numbers on non-food contact surfaces

• Floor next to deli drain• Pre-op: 4x104, 3x102, and 2.5x105/sponge

(total of 3 stores)• During operation: <10; 1x105/sponge (2

stores)• Cold room floor or drain

• During operation: 5x106, 1x106, 3x101/sponge (3 stores)

May 22nd, 2013Interagency Risk Assessment--Listeria monocytogenes in Retail Delicatessens Public Meeting

L. monocytogenes and Listeria spp. testing

19

Among a total of 4,512 samples:• 3,980 (88.2%) samples negative for both LM and Listeria

spp.• 291 (6.4%) samples positive for LM only• 133 (2.9%) samples positive for LM and Listeria spp.• 108 (2.4%) samples positive for Listeria spp. Only

Data indicate that L. monocytogenes testing will facilitate focus on actual food safety hazard

• Some stores show presence of indictor, but not the pathogen

May 22nd, 2013Interagency Risk Assessment--Listeria monocytogenes in Retail Delicatessens Public Meeting

Summary and conclusions• L. monocytogenes contamination in retail

environments non-food contact surfaces is not uncommon– L. monocytogenes is common in surrounding environments– L. monocytogenes contamination of FCS is considerably

less than contamination of non-FCS– Wide variation in L. monocytogenes prevalence among

stores• L. monocytogenes persist widely in retail

environments (>35%)– Need to control niches

• Focus on L. monocytogenes testing rather than Listeria spp. testing is warranted at retail

20May 22nd, 2013Interagency Risk Assessment--Listeria monocytogenes in Retail Delicatessens Public Meeting

Acknowledgments

Students and staff: S. Roof, S. Warchocki, E. Fortes, E. Wright, C. Simmons, B. Ziegler, S. Chambers, E. Christian, P. Cook, J. Wang, C. Wickware, A. Pleitner, N. Donovan, N. Boyd, J. Eichinger, L. Hill, J. Wang, S. Hammons

Collaborators: Retailers, New York State Department of Agriculture and Markets, Neogen Corp., Ecolab

Financial support: USDA, Food Safety and Inspection Service/Office of Public Health Science Food Marketing Institute Foundation American Meat Institute Foundation

21May 22nd, 2013Interagency Risk Assessment--Listeria monocytogenes in Retail Delicatessens Public Meeting