Seek and Destroy: Best Practices for Controlling Environmental Pathogens

“If you cannot define what you are doing as a process, you do not understand what you are doing.” — W. Edwards Deming

The purpose of this article is to share over 30 years of best practices developed in the area of environmental pathogen control. The focus is Listeria, but the practices and principles apply broadly to organisms harbored in our environment.

Many of these best practices were learned at some expense, many failures, and just plain tenacity. There are no silver bullets, but experience has shown that microbiological control of food processing environments can be attained. Every plant is different because the inherent microbiological risks are different even though equipment, procedures, processes, and products may be the same.

A Basis for Process Control

The theory of food safety process control has its basis in risk identification, science, and management. The challenges of environmental microbiological process control are daunting because there is no kill step to intervene. Root cause analysis produces three primary results:

Pillars of Control

  1. Eliminate harborage sites in exposed product areas.
  2. Control transfer of the organism.
  3. Deploy process management techniques to control the environment.

Persistent resident pathogen strains must be removed from the exposed product production process even if there is not a kill step in the product production process. The Seek and Destroy Process started as an investigative method to assess the sanitation of and locate harborage sites in equipment. Today, it represents the totality of establishments’ overall microbiological sanitation process control efforts. This includes verification of control as well as measurements of process control. Most companies producing ready-to-eat (RTE) products deploy a pathogen environmental monitoring (PEM) program. Typically, sampling occurs during production with the intent to verify the absence of the organism. The PEM is an effect measure and trailing indicator of risk.

Verification monitoring program. This is a routine program to verify the effectiveness of the sanitation process control program that includes sampling of Zone 1, 2, and 3 environmental sites in the RTE area. This program is used for regulatory compliance.

Monitoring of verification sites detects the organism as it is being moved from its harborage location to a contact surface or the product. Verification sites are surfaces that are exposed during the normal operating conditions and are likely to serve as transfer points (i.e., they are located in transfer pathways). If an exposed surface is suspected to be a harborage site, then preoperative sampling should be used to measure the effectiveness of the sanitation process. Sanitation effectiveness of exposed surfaces needs to be validated with preoperative sampling then monitoring (APC) to verify effectiveness. Verification type sampling is used by USDA Food Safety Inspection Service in its RLm events as well as FDA in its “Swabathons” sampling events.

The S&D Process is a method for not only verifying the effectiveness of the sanitation process control program, but also sampling to measure preventive controls such as investigative (not-for-cause) sampling to define levels of disassembly, identification of indicator sites, qualification of new equipment, measure effectiveness of hurdles and barriers, and measurement of potential risk from Zone 4 areas.

Engage Your Employees

The development and sustained deployment of best practices requires employee engagement—teamwork is the pathway to success. I strongly encourage the development of a team to be the responsible and accountable force to implement and deploy environmental control best practices at each plant site (see Figure 1).

Our team is called the “Seek & Destroy” Team. Below are our model team charters using the elements of purpose, methods, and the results expected.

Team meetings. These meetings are not committee meetings to discuss why GMPs are not working. Lengthy notes are not expected nor wanted. Instead the focus is on action taken to accomplish the results expected.

Task team leaders report progress and identify any roadblocks to success, which become key issues for resolution. These may be solvable within the team (vested authority to make change is a critical component of each team member’s responsibility); those that cannot must be addressed by team leadership, or plant and/or corporate management.

Action taken on roadblocks is reported in the team’s action log or action register. Transparency and communication of solutions to roadblocks and best practices implemented are needed to reinforce the preventive mindset of the organization.

Management, quality, and maintenance must all hold one another accountable for timely action on roadblocks, and each has a specific role to fill.

  1. Management’s role: Management must support team training and provide facilitation when needed. Team members’ time must be allocated appropriately—this is another reason to keep the scope very narrow and address the most significant risks. The management systems of SOP, SSOP, operational procedures, and work instructions must support the documentation, training, and implementation of changes made by the team. In addition, management must not let the team “boil the ocean”—focus and execution are keys to success.
  2. Quality’s role: Audits are designed by quality management to recognize changes made and to hold gains.
  3. Maintenance’s role: The maintenance PM system is most often the ideal way of managing simple changes. The team leader and maintenance/engineering members can input and create work orders to address the types of problems that are encountered. Periodic infrastructure cleaning (PIC) and periodic equipment cleaning (PEC) are often best managed with the maintenance PM system.

Teams and teamwork best practices. It’s a good idea to rotate team leader and team members to create greater buy-in within the workforce. Take pictures and tell stories to onboard and engage new team members. They will spread and be used as a basis for the normal and accepted behavior.

Be sure to keep the team charter simple—two pages maximum. The charter should identify the team as the accountable body within the facility to define and implement process control measures. Management must support this concept and approach, and provide resources.

The determination of results expected is broken into smaller tasks. Assigned task teams are typically led by an S&D Team member. Task teams are small but employ key affected parties for solutions and implementations. The implementation of recognized best practices eliminates needless research and firefighting.

Teamwork enables the plant organization as a whole to have a much deeper understanding of “why” certain procedures exist as well as how to follow data and to use it to hold gains. “Why” is a driver of the process—a key to sustainability.

Eliminate Harborage

growth niche is defined as a location that supports microbiological growth and is protected from the sanitation process; it is characterized by high microbial counts after normal cleaning and sanitation. A harborage site is defined as a growth niche that contains the pathogen or its indicator. (For a complete list of Environmental Monitoring Operational Definitions see the 3M Environmental Monitoring Handbook 1st Edition.)

The slide image has been used in the (North) American Meat Institute’s Listeria Intervention and Control workshop for almost two decades. The conveyor picture is from Bruce Tompkin, PhD (retired from ConAgra Foods). This is classic because hollow rollers have been and continue to be one of the greater nemeses of the food industry. A classic mode of contamination and recontamination occurs during every cleaning cycle during the initial rinse. The rinse down and removal of product debris unfortunately enables food, water, and microorganisms to penetrate the hollow member, making the bacteria protected from the cleaning and sanitizing chemicals. Further rinsing only provides more water for growth. Land O’ Frost and I found the depth and degree of penetration is directly correlated to the force of the rinse water. High pressure used during sanitation is a major cause of sanitary design issues becoming growth niches and harborage sites.

No Niches. According to (North) American Meat Institute’s (N)AMI’s Equipment Design Task Force, “All parts of the equipment shall be free of niches such as pits, cracks, corrosion, recesses, open seams, gaps, lap seams, protruding ledges, inside threads, bolt rivets and dead ends. All welds must be continuous and fully penetrating.”

The method to identify growth niches and harborage sites is the Seek and Destroy investigation, which is used to find pathogenic growth niches, find potential growth niches requiring monitoring and control, define normal level of disassembly, define periodic deep levels of disassembly, define the frequency of periodic deep levels of disassembly, qualify a new piece of equipment (usually, run for 90 days then conduct Seek and Destroy Investigation); validate effectiveness of equipment cleaning protocol; and validate effectiveness of intervention applied to a piece of equipment (heat treatment or other method).

The sanitary design of the equipment during disassembly may be evaluated using the (North) American Meat Institute Equipment Design Task Force Checklist or another method.

In a Seek and Destroy Investigation:

  1. Pre-number or pre-code sample collection bags.
  2. Take a picture of the bag to indicate the next sample site to be taken.
    1. Get a distance picture to locate the site within the plant area. Take several more pictures up to a closeup of the site itself.
    1. Document the name of the site. Typically a maintenance person is the best resource for properly naming sites.
  3. Repeat step 2 with each consecutive site

Understanding Movement

The movement of people, equipment, product, and materials during production operations provides motility for organisms—they move along a pathway by vectors from transfer point to transfer point. Movement from a harborage site also occurs deep within equipment or facility to the exposed processing environment. Sampling during production finds the organism moving from its preoperational state to a contact surface, the product, or a drain. The process flow of the vectors dictates the direction of movement.

Disruptive events such as rinse down at breaks even with sanitizer may physically remove many organisms from equipment. However, this activity does not eliminate the organism from the environment. Rinsing does relocate the organism, however, providing more pathways of movement.

Verification sampling during production of Z1, Z2 and Z3 pathways verifies the ability of the sanitation process control to minimize the transfer and movement of the organism.

To prevent or minimize movement, create a torturous pathway that maintains a high concentration of sanitizer on the floor and includes hurdles such as sole scrubbers between hygienic zones. Also consider captive footware, separation and segregation of transport equipment, and keeping floors dry.

Implement a Process Control for Environmental Pathogens

The final pillar of environmental pathogen controldefines how the gains are being held while continuing the risk reduction process. The cost of pathogen sampling has and continues to drop. Pathogen sampling of verification and indicator sites are composited. History and data analysis have identified those most optimal and risky areas to sample on a regular basis. Not-for-cause investigations continue ensuring any process changes are done without increasing microbial risk. APC testing is fine tuned to recognize any shifts in the environment. Shifts that are found lead to the application of interventions and aggressive sampling.

The visual of the S&D Process as a whole is presented in the Figure 3 flow chart.

S&D Process best practices—process control (not-for-cause) investigation. The S&D Process can be conducted in situations where food safety has not been compromised. Examples include when samples are taken to find a new growth niche, find a new transfer vector/pathway, establish or qualify a hurdle or barrier system, establish a monitoring procedure or process, and assess or characterize risk of a control procedure, part of facility or process change.

Investigations can also be triggered by an indicator site positive. This becomes part of the aggressive sampling following an indicator out of control observation. These indicator sites are strategically located in close proximity to a known growth niche, barrier or hurdle. Movement of the organism from the indicator site through a verification site or area would be required before violation of food safety. These indicator sites over time measure the strength of the barrier or hurdle or the effectiveness of the management of growth niches.

In addition, a Seek and Destroy Investigation can be conducted on a new piece of equipment to develop sanitation methods and identify potential areas of risk and on a piece of equipment to define the normal and periodic deep level of disassembly.
Investigative sampling to identify optimal locations for placement of indicator sites in either Z3 or Z4, and measurement of risk in Z4 area are also acceptable.

Indicator sites. Indicator sites are the measurement system for a microbiological process control. They are “risk-based” indicators of special causes or process shifts in the environment.

Ideal indicator sites include locations close to the growth niche that can identify an active growth niche, locations that can identify suspect organisms before they become attached to or imbedded within the equipment, Z4 to Z3 Transfer areas, and Sanitary Facility & Equipment Design issues.

Post rinse. Post-rinse sampling is an indicator for potential risk. Positive post-rinse sampling is not an indicator of a food safety hazard, however. Typical sites are below the product line and in areas that tend to collect spatter from the rinsing process (e.g., machine sides, legs, support structure, floor wall juncture). Detection of the organism does not mean there is a harborage site within the scope of the sampled area. Positive post-rinse samples will typically trigger aggressive sampling or not-for-cause investigative sampling. Post rinse 10 days in a row.

Sample large areas that collect “spatter.” Composite sampling is acceptable. Positive results will direct investigation team to a line, pair of lines, or section on a line.

The S&D Process quick tips.

  • Measurement system
    • APC to manage growth niches
    • APC at Preop to measure effectiveness of sanitation
      • Expect 99 percent large area swabs (Plant KPI) to be < 100 cfu (total area)
  • Continuously seek indicator sites
  • Increase percentage of indicator sites to verification sites by adding indicator sites as the process evolves and data is collected
  • Reward finding positives
  • Seek and Destroy Investigation on a piece of equipment that has been in operation without any linked verification positives to measure the effectiveness of sanitation methods below the normal level of disassembly

Maturity Models

Maturity models are used in the S&D Process to define the stages or levels of control attained. The stages include Awareness, Enlightenment, Preventive, and Predictive.

Awareness & Enlightenment are characterized by repeated positives in the same general areas: firefighting and a failure to find and eliminate or manage the harborage site(s). Failure to effectively use or deploy preventative practices keeps the establishment in a “firefighting state.” In this state, management promotes not getting to the root cause and rewards solving the same problem over and over again.

The S&D Process moves the establishment along the journey from the Awareness Stage to the Predictive Stage. The establishment transcends to the Preventive Stage when harborage sites are eliminated through redesign or managed with an intervention capable of eliminating the pathogen from the harborage site. The Predictive Stage evolves as data is used to predict when to apply interventions and other more aggressive preventive controls.

I see the elements of our maturity models changing as technological advances occur in metagenomics, rapid methods, and broader application of whole genome sequencing. These technologies are reducing the time for identification of outbreaks as well as detecting smaller events. Time compression is and will continue to occur at the processor level to identify, eliminate, or manage harborages.

Dr. Butts, a member of Food Quality & Safety’s Editorial Advisory Panel, is founder and president of FoodSafetyByDesign, LLC, and advisor to CEO Land O’ Frost. Reach him