Published on March 11, 2014
Sanitary Control of Listeria monocytogenes in the Poultry Processing Environment Leslie Thompson, Ph.D. Department of Animal and Food Sciences Texas Tech University
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
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
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
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
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
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
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
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
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
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/
Potential Contamination Sources • Employees (gloves, boots, aprons) • Incoming air • Raw materials (Raw chicken) • Soil • Water • Processing environment
Potential Contamination Sources • LM persistence in processing niches • Floors • Drains • Standing water • Hollow rollers • Hollow equipment frames
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
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
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
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
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
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
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
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
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
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
Control of LM in the Processing Environment • Alternative 3 is a higher risk environment FSIS, 2012
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
Thank you for your time and attention!
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.
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.
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