This document discusses Listeria monocytogenes (LM) control in poultry processing environments. LM is a pathogenic bacteria that causes listeriosis, a serious disease with high mortality rates. The document outlines the characteristics of LM, including its ability to form biofilms and persist in processing plants. It describes strategies to control LM in ready-to-eat foods, including the use of post-lethality treatments, antimicrobials, or sanitation programs. The document provides detailed guidance on sanitation practices for controlling LM, including pre-operational cleaning and sanitizing, operational sanitation procedures, environmental sampling plans, and controlling cross-contamination. Effective control of LM requires a comprehensive sanitation program with a focus on preventing

1. Sanitary Control of Listeria monocytogenes
in the Poultry Processing Environment
Leslie Thompson, Ph.D.
Department of Animal and Food Sciences
Texas Tech University

2. Why the Concern over Listeriosis?
• Rare but serious foodborne disease
• 20 to 30% mortality
• Opportunistic pathogen for at-risk-
populations
• Immunosuppressed
• Pregnant women
• Unborn or newly born
• Elderly

3. Listeriosis Characteristics
• 1980s foods recognized as primary route
of transmission for human listeriosis
• Clinically two categories of disease
• Non-invasive – febrile gastroenteritis
– Onset a few hours to 2 to 3 days
• Invasive – septicemia, encephalitis, meningitis,
spontaneous abortion, death
– Onset 3 days to 3 months

4. Listeriosis Characteristics
• First observed in industrialized nations
• Mostly associated with ready-to-eat foods
(RTE)
• Many foods associated with outbreaks
have 103 CFU of LM/g or greater

5. Listeriosis Characteristics
• Implicated foods:
 Raw or inadequately pasteurized milk, chocolate milk,
ice cream,
 Cheese (queso fresco in particular)
 Raw vegetables
 Raw and smoked fish
 Raw poultry and meat
 Deli meats and hot dogs
WHO and FAO, 2004

6. Survival and Growth Characteristics of Listeria
monocytogenes
• Extremely hardy
• Facultative anaerobe (grows with or without
oxygen)
• Salt-tolerant (Survives salt challenge of 25.5%)
• Attaches to surfaces to form difficult-to-remove
biofilms
• More resistant to sanitizers when in a biofilm

7. Listeria monocytogenes Characteristics
• Habitat: Ubiquitous, found in soil, moist
environments, decaying vegetation, silage,
fecal material, air, dust
• Psychrophilic – grows well under
refrigeration
• Grows well in cool, damp environments

8. Listeria monocytogenes Characteristics
• More heat resistant than most foodborne
pathogens
• Survives freezing and drying
• Resists nitrates, high salt levels and acid
• Can grow in vacuum package
• Known for it’s persistence in food
manufacturing environments

9. Growth Limits for Listeria monocytogenes
Characteristic Minimum Optimal Maximum
Temperature
(°C)
-1.5 37 50
pH 4.3 7.0 9.6
Water activity 0.92 NA NA
USDA-FSIS, 2012, and Donnelly, 2001

10. Listeria monocytogenes Characteristics
• Can establishes niche or harborage site
• LM can be spread from harborage site to
food contact surfaces and product
• Cornerstone of control is a well-designed
sanitation program

11. Foods of Greatest Concern
• Ready-to-eat (RTE) foods with
characteristics of:
 Support the growth of LM
 Have a long refrigerated shelf-life
 Consumed without further listericidal treatment
FAO/WHO, 2004a, b
http://www.foodsafetymagazine.com/magazine-archive1/octobernovember-2010/listeria-
monocytogenes-controlling-the-hazard-in-rte-meat-and-poultry-processing-environments/

12. Potential Contamination Sources
• Employees (gloves, boots, aprons)
• Incoming air
• Raw materials (Raw chicken)
• Soil
• Water
• Processing environment

13. Potential Contamination Sources
• LM persistence in processing niches
• Floors
• Drains
• Standing water
• Hollow rollers
• Hollow equipment frames

14. Improved Public Health Can Be
Achieved Relative to LM
Reducing the occurrence of LM in
manufacturing and retailing of foods that
don’t support it’s growth
FAO/WHO, 2004a, b

15. Improved Public Health Can be
Achieved Related to LM
• In foods that support LM growth
 Control measures
• Better temperature control
• Limiting length of storage period
• Managing the post-lethality treatment environment
 Reformulation of foods so they don’t support the growth
of LM
 Use of a combination of interventions in post-lethality
exposed foods
WHO and FAO, 2004 and FSIS, 2012

16. Controlling LM in Ready-to-Eat
Foods
• Focus is on RTE meat and poultry
products
• USDA - Food Safety Inspection Service
Compliance Guideline – 2012
“Controlling Listeria monocytogenes in post-
lethality exposed RTE Meat and Poultry
Products”
FSIS, 2012

17. Controlling LM in RTEs
• “Zero tolerance” of LM in ready-to-eat
meat and poultry products (USDA-FSIS 9
CFR Part 430, the Listeria Rule)
• RTE products are considered adulterated
if they come in contact with LM or a food
contact surface (FCS) that is contaminated
with LM
FSIS, 2012

18. Incorporation of One of Three
Strategies to Control LM in RTEs
• Alternative 1
 Employ both:
• post-lethality treatment that reduces or eliminates LM,
and
• use of an antimicrobial agent (i.e. sodium diacetate or
potassium lactate) or a process (i.e. freezing) to
suppress or limit the growth of LM that functions
during the shelf-life of the product.
 Verification focus is on post-lethality treatment.
Sanitation is important still however.
FSIS, 2012

19. Incorporation of One of Three
Strategies to Control LM in RTEs
• Alternative 2
 Employ a post-lethality treatment or an antimicrobial
agent or process.
 Sanitation program must include testing of post-lethality
food contact surfaces. Establishments are subject to
more frequent verification activities compared to
Alternative 1.
FSIS, 2012

20. Incorporation of One of Three
Strategies to Control LM in RTEs
• Alternative 3
 No post-process lethality treatment, no antimicrobial or
no antimicrobial process. Relies only on sanitation
program.
• Specific focus on measures which can be
incorporated into the HACCP plan. SSOP’s and other
prerequisite programs control LM.
• Sanitation program must include testing of food
contact surfaces. Establishments are targeted for the
most verification activities compared to Alternative 1
and 2. FSIS, 2012

21. Listeria Control Guideline
1. Determine if product is RTE
Is there a standard identity that product is
fully cooked? Deli meats and hotdog
products, salads, spreads, fully cooked
sausages
FSIS, 2012

22. Listeria Control Guideline
2. Determine if product is post-lethality
exposed?
 Is product exposed to environment post cooking during
further processing as in slicing, peeling, freezing,
packaging?
 Is product removed from cook bag to slice or
repackage?
 Fermented or acidified, salt cured or dried and smoked
product that is packaged after application of process.
FSIS, 2012

23. Listeria Control Guideline
3. Determine if product is covered by Listeria
Rule
 If product is RTE and post-lethality exposed, then
subject to Listeria Rule
 If product is RTE but doesn’t have post-lethality
exposure then not subject to Listeria Rule
 If not RTE then not subject to Listeria Rule
FSIS, 2012

24. Control of LM in the Processing
Environment
• Alternative 3 is a higher risk environment
FSIS, 2012

25. Critical Components of an Effective
LM Sanitation Program
Four key components
• Pre-operational cleaning and sanitizing
that are effective in preventing LM from
forming niche sites in processing
environment
• Operational sanitation to prevent cross-
contamination in the RTE processing
environment
FSIS, 2012

26. Critical Components of an Effective
LM Sanitation Program
• Intensified cleaning and sanitizing
procedures when LM-positive sampling
results occur
• Documentation and verification of cleaning
and sanitizing procedures
FSIS, 2012

27. LM Niche or Harborage
• An area where Listeria has grown to high
numbers within the plant
• LM can be distributed from harborage to
food contact surface or product surface
FSIS, 2012

28. Factors Affecting Niche Formation
• Equipment design
• Construction activities
• Operational conditions that move product to
difficult to clean areas
• Mid-shift cleaning and sanitizing
• Poor use of high pressure during cleaning
• Product characteristics that require excessive
rinsing FSIS, 2012

29. Niche Sites in Processing
Environment
• Drains, floors
• Hollow rollers on
conveyors
• Valves
• Worn and cracked rubber
seals
• Vacuum or air pressure
pumps
• Air Filters
• Cleaning tools
• Boots
• Ice makers
• Trash cans
• Cracked hoses
• Wet insulation
• Fork lifts
• Pallets
• Hollow frame work
• Maintenance tools
FSIS, 2012

30. Niche Sites in Processing
Environment
• Chiller shelves
• Roller guards
• Passage ways
• Standing water
• Pallet jacks
• Equipment lubricants
• Space between close
fitting plastic-to-metal
parts or metal-to-metal
• Packing equipment
• Packaging film or
wrappers
• Chilling solutions
including brines
• Peelers, slicers,
shredders, blenders,
scales, casing removal
equipment
• Bins, tubs, totes
FSIS, 2012

31. Cleaning and Sanitizing
Cleaning – Removal of
visible soil
• Dry and wet
• Cleaning agents
• Tools – Separate for food
contact surfaces and non-
food contact surfaces
• Temperature, contact
times, match soil types
with cleaning agent
Sanitizing – Reduction of
harmful microorganisms to
safe levels
• Surface must be clean
first
• Use heat or chemicals
• Follow manufacturer’s
directions
• Time, temperature,
concentration and pH are
critical

32. Pre-Operational Cleaning and Sanitizing
Nine Steps
1. Dry cleaning – Remove solid materials,
disassemble equipment such as slicers and
dicers – floors, conveyor belts and tables
2. Wash and rinse floor
3. Pre-rinse equipment (in same direction as
product flow) warm or cool water ≤60°C. Temps
above 60°C can bake soils on the surface
making them more difficult to remove.
FSIS, 2012

33. Pre-operational Cleaning and Sanitizing
4. Clean, foam and scrub equipment with minimum
recommended contact time (5 to 25 min)
5. Rinse equipment (in same direction as product
flow)
6. Visually inspect equipment to identify residues,
re-clean areas as needed
FSIS, 2012

34. Pre-operational Cleaning and Sanitizing
7. Sanitize floor, then equipment
 Avoid contaminating equipment with aerosols from floor
 Caution with high pressure hoses
 Use hot water ≥ 82.2°C for 10 sec
 Acidic quaternary ammonia
 Steam not very effective on LM
8. Rotate sanitizers periodically. Alternate
between alkaline and acid-based detergents.
For example: Alternate between neutral and acid
quaternary ammonia FSIS, 2012

35. Pre-operational Cleaning and Sanitizing
9. Dry
 Air drying
 Reduce relative humidity if possible
 Squeegees
 Avoid cross-contamination from splash from non-food
contact to food-contact surfaces
FSIS, 2012

36. Sanitizer Considerations for Inactivating LM
Biofilms
• Chlorine and iodophors not effective on LM
biofilms
• Most effective sanitizers on LM biofilms are acid
quaternary ammonia, peracetic acid, chlorine
dioxide
• Neutral quaternary ammonia compounds not
very effective
FSIS, 2012

37. Operational Sanitation Procedures
1. Control air temperature and air handling
units
 Maintain cold temp in packaging room ≤10°C
 Monitor temps
 Use positive air pressure out of the RTE room into the
raw room
 Clean air handlers and cooling units periodically
 Immediately correct condensation or standing water
problems in RTE rooms. Stop production during repair.
Clean and sanitize after repair.
FSIS, 2012

38. Operational Sanitation Procedures
2. Equipment Design and Maintenance
• Maintain equipment properly and routinely
• Use lubricants that have listericidal additives
such as sodium benzoate
• Clean maintenance tools on a regular basis. If
possible have separate tools for raw and RTE
rooms and equipment
FSIS, 2012

39. American Meat Institute Principles for Sanitary
Design of Facilities and Equipment
• Ten Principles of Sanitary Design
 Cleanable to a microbiological level
 Made of compatible materials
 Accessible for inspection, maintenance,
cleaning and sanitation
 No product or liquid collection
 Hollow areas hermetically sealed

40. American Meat Institute Principles for Sanitary
Design of Facilities and Equipment
Ten Principles of Sanitary Design, continued
 No niches
 Sanitary operational performance
 Hygienic design of maintenance enclosures
 Hygienic compatibility with other plant systems
 Validated cleaning and sanitizing protocols

41. Operational Sanitation Procedures
3. Traffic Control
• Imperative to control movement of personnel
and raw product to prevent cross-contamination
of RTE products and food contact surfaces in
post-lethality areas.
• Create traffic patterns that prohibit the
movement of product, equipment and personnel
between raw and RTE areas.
FSIS, 2012

42. Operational Sanitation Procedures
3. Traffic Control, continued
Employees should not work in both raw and RTE
areas!
If they must:
• Change outer clothing (aprons, coats, hard hats
and soiled clothes)
• Wash and sanitize hands
• Clean and sanitize boots
FSIS, 2012

43. Operational Sanitation Procedures
3. Traffic Control, continued
• Use airlocks or vestibules between raw and RTE
areas
• Use foam sanitizing sprays on either side of RTE
doors
• Foot baths are not the best option, but if used
change frequently, use 400 to 800 ppm quats,
minimum 5-cm depth, chlorine is not effective.
FSIS, 2012

44. Operational Sanitation Procedures
4. Employee Hygiene
• Handwashing for a minimum of 20 sec:
 After restroom use
 Before entering work area
 When leaving the work area
 Before handling product
FSIS, 2012

45. Operational Sanitation Procedures
4. Employee Hygiene, continued
• Gloves
 Wash hands before applying gloves
 RTE gloves should be disposable
 Dispose of glove after touching non-food contact surface
 Dispose of gloves upon leaving processing line
FSIS, 2012

46. Operational Sanitation Procedures
4. Employee Hygiene, continued
• Remove coats, gloves, sleeves, and outer clothing when
leaving RTE areas
• Coats, gloves, sleeves, and outer clothing should never
be worn in restrooms, eating areas, or left in lockers
• Do not eat in locker rooms or store food in lockers
• Do not store tools, knives or other equipment in
personal lockers
FSIS, 2012

47. Operational Sanitation Procedures
4. Employee Hygiene, continued
• Have separate cleaning crews for raw and RTE
areas
• Train, monitor and verify employees in proper
hygiene practices
• Maintenance employees and tools pose a
special risk
FSIS, 2012

48. Operational Sanitation Procedures
5. Controlling Cross-Contamination
• Rodent and insect control
• Eliminate standing water
• Discard product that touches non-food contact
surfaces
• Use separate pallets for raw and RTE areas,
color coded
• Avoid condensation
FSIS, 2012

49. Operational Sanitation Procedures
5. Controlling Cross-contamination, continued
• Do not use high pressure sprays near exposed
RTE product
• Drains from raw or “dirty” side should not be
connected to drains on cooked or “clean” side of
plant
FSIS, 2012

50. American Meat Institute Principles for Sanitary
Design of Facilities and Equipment
• Three broad themes:
 Provide zones of control
 Keep it cold and moisture control
 Equipment and facility design to facilitate
sanitation
FSIS, 2012

51. Environmental Sampling Plan
• Four zones of focus. Zones are based on
level of risk to product contamination:
 Zone 1 – Food product contact surfaces such as belts,
conveyors, etc.
 Zone 2 – Equipment surfaces close to the food contact
surfaces such as control buttons, equipment framework,
mechanic’s tools
FSIS, 2012

52. Environmental Sampling Plan
• Four zones of focus, continued:
 Zone 3 – Surfaces not in direct contact with food or
surfaces that are close to food contact surfaces (floors,
walls, ceilings, floor mats, pallets, forklifts, pallet jacks)
 Zone 4 – Areas distant from production areas
(restrooms, loading dock, hallways, warehouses,
coolers, break rooms, locker rooms)
FSIS, 2012

53. Environmental Sampling Plan
• For a processing environment not in
control of LM focus on Zone 1 first.
• Once Zone one compliance is
demonstrated expand focus to Zones 2, 3
and 4.
FSIS, 2012

54. Hold and Release Program
• Need a “Hold and Release Program” in the
event a positive test occurs
• Need a plan for corrective actions
FSIS, 2012

55. Conclusions
• Current technology is not possible to
totally eliminate LM
• Raw product is likely the source of LM in a
plant (USDA, 2010)
• Focus on preventing post-lethality
environment
• Sanitation practices are key
FSIS, 2012

56. Thank you for your time and attention!

57. References
Berrang, M.E., R.J. Meinersmann, J.F. Frank, D.P. Smith and L.L. Genzlinger. 2005.
Distribution of Listeria monocytogenes subtypes within a poultry further processing
plant. J. Food Prot. 68(5):980-985.
Donnelly, C.W. 2001. Listeria monocytogenes: A continuing challenge. Nutrition Reviews
59(6):183-194.
FAO/WHO. 2004a. Risk assessment of Listeria monocytogenes in ready-to-eat foods.
Microbiological Risk Assessment Series 4. Technical Report. Food and Agriculture
Organization and the World Health Organization. Geneva, Switzerland.
FAO/WHO. 2004b. Risk assessment of Listeria monocytogenes in ready-to-eat foods.
Microbiological Risk Assessment Series 5. Food and Agriculture Organization and the
World Health Organization. Geneva, Switzerland.
FDA. 2012. Bad bug book. Foodborne pathogenic microorganisms and natural toxins
handbook, 2nd Ed. Center for Food Safety and Applied Nutrition (CFSAN) of the Food
and Drug Administration, U.S. Department of Health and Human Services
Lianou, A., and J.N. Sofos. 2007. A review of the incidence and transmission of Listeria
monocytogenes in ready-to-eat products in retail and food service environments. J.
Food Prot. 70(9):2172-2198.

58. References
USDA-FSIS. 2012. FSIS compliance guideline. Controlling Listeria monocytogenes in
post-lethality exposed ready-to-eat meat and poultry products. United States
Department of Agriculture, Food Safety and Inspection Service.