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

Figure 1. Classical Pathogen Environmental Monitoring
Image credit: FoodSafetyByDesign, LLC

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.