Listeria monocytogenes Prevalence, Persistence, and Control

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Listeria monocytogenes Prevalence, Persistence,
and Control
Haley F. Oliver, Ph.D. Associate Professor Purdue
University
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Oliver Lab Listeria and Retail

• Objective
• Improve public health through evidence-based
  interventions to control Listeria monocytogenes.
• Strategies
• Collaborate with retailers sanitation providers
• Locate environmental niches
• Determine transient vs. persistent contamination
• Test alternative sanitation procedures
• Identify best practices
• Develop long-term practical controls

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Longitudinal study of deli environments
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Conclusions From Longitudinal Study

• LM can be prevalent in retail delis (10-40)
• LM can persist in retail delis (observed 1.5
  years)
• LM does not persist in all stores (only11/30
  observed)
• Non-food contact surfaces have higher LM
  prevalence than food contact surfaces (NFCS 15
  vs. FCS 4)

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Phase 3 -- Intervention

• SSOP Transfer Points
• Deli case handle
• Cold room door handle
• Slicer adjustment knobs and handles
• Scale top keypad
• Floors
• General floor cleaning
• Floor wall juncture
• Drains surface. Each retailers will retain
  current protocols for drain management
• Single and 3 basin sinks
• General floor cleaning
• Floor wall juncture 
• Deli Case Food Contact Surfaces
• Deli case trays
• Opened product (i.e. in-use product) display
  shelving
• Slide and display doors 

• Deli Case Down to the Coils
• Entire deli case (not in sections see FMI
  protocol)
• Slicers, Handles, and Knobs
• Entire slicer
• FCS including blade, guards, and slicer case
  under the blade 
• Additional Actions/SOPs
• Squeegee 
• High Pressure Hoses (i.e. spray nozzle/spray gun
  style) 
• Training
• Verification/ATP Testing
• Survey

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Previous Longitudinal Study
Pre-Intervention Post-Intervention
Food Contact 63/1595 (4.0) 63/1595 (4.0)
Transfer Point 18/540 (3.3) 18/540 (3.3)
Non-Food Contact 334/2368 (14.1) 369/2360 (15.6)
Overall 425/4512 (9.4) 450/4495 (10.0)

• 17/30 stores show low LM prevalence (lt5)
• 5/30 stores show moderate LM prevalence (5-10)
• 8/30 stores show high LM prevalence (10)
• 11/30 stores show evidence for persistence

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  April May June July August September October November December
Food 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 LM CU-258,69 CU-258,69
1-basin sink exterior NT NT NT CU-258,69 - - LM - CU-258,69
Floor/wall junction (1-basin) NT NT NT CU-258,69 - - LM CU-258,69 CU-258,69
Deli drain NT NT NT CU-258,69 CU-258,333 - CU-258,69 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
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 - - - - - -
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Aggressive Deep Cleans

• Goal To adapt and execute manufacturing-based
  mitigation strategies in retail delis
• Method
• 12-16 hour overnight shutdown
• 10-20 person crew
• Remove products
• Disassemble equipment
• Clean and sanitize all surfaces

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Overnight Deep Clean Protocol
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Interventions by Store
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Longitudinal Efficacy

• Reduced average monthly LM prevalence a mean 9.7
  percentage points (CI95 2.50, 16.90 p0.017)
  per store.

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• Employee-executed deep cleans with training were
  more effective for long-term control than third
  party execution of the same protocol.

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• Whole-genome sequencing shines a new light in
  this area that helps us find unsuspected gaps in
  the food safety system this is a wake-up call to
  the ice cream industry in general and to the
  regulators.
• Robert Tauxe, CDC
• DOI 10.1126/science.aac4551

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L. monocytogenes WHOLE GENOME SEQUENCING PROJECT

• In the first year of the project, integrating WGS
  with other Listeria surveillance activities
• Improved detection of listeriosis clusters.
• Increased the number of outbreaks solved.
• Reduced the average cluster size.
• One persons listeriosis infection was linked to
  prepackaged lettuce. Prior to WGS it would have
  been almost impossible to make a link between the
  contaminated food and one person who was not part
  of an outbreak.
• December 2014 identified caramel apples as
  source of large listeriosis outbreak. WGS
  identified the illnesses one week faster than
  would have occurred with PFGE alone.

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L. monocytogenes WHOLE GENOME SEQUENCING PROJECT
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Whole Genome Sequencing improves Identification
of persistent LM in retail

1. apply single-nucleotide polymorphism (SNP)-based
   phylogenetics to subtype
2. to differentiate persistent from repeatedly
   reintroduced strains
3. identify genetic determinants of L.
   monocytogenes persistence

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NGS technologies

• Illumina MiSeq and HiSeq platforms
• Solid state amplification
• Single- and paired-end reading (resolve ambiguous
  alignment)
• Use of Solexa chemistry for fluorescent labeling
• Read lengths of 300bp (MiSeq) and 125bp (HiSeq)
• Read quantity up to 25million (MiSeq) and
  2billion (HiSeq)

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WGS

• Unique to a single retail deli, supporting
  persistence within the deli
• Unique to a single state, supporting clonal
  spread within a state
• In 13 events, nearly indistinguishable isolates
  (0 to 1 SNP) were found across multiple delis

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PFGE WGS
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• Now that were turning whole-genome sequencing
  on, were identifying outbreak after
  outbreakwere also finding smaller outbreaks
  that we werent able to find before.
• Brendan Jackson, CDC
• DOI 10.1126/science.aac4551

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Current Work

• USDA-NIFA-AFRI 2015-05673
• Prevalence, Persistence and Control Strategies
  of Listeria ssp. and Salmonella in Retail Grocery
  Produce Storage and Sales Environments

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