Testing Services, Thought Leadership

How to Develop an Environmental Monitoring Program for Listeria

environmental monitoring program

Why an Environmental Monitoring Program is Needed

Listeria is incredibly common, and because of its prevalent nature, it can easily be introduced into your facility. In addition to that, it is a tough survivor even under adverse conditions. It can grow even in cold environments — one of the few foodborne pathogens able to do so.

Environmental conditions that could result in contamination exist throughout the production line and during transmission to a facility. Potential sources include soil from the production environment; unprotected contact from employees and visitors; incoming raw materials and ingredients; food production equipment and utensils; and poor ventilation that allows for dust build-up and condensation.

Therefore, it’s important to have an environmental monitoring program in place that considers all high-risk modes of contamination and cross-contamination in order to catch and eradicate Listeria before it becomes a public safety concern.

Create a Written Plan

Documenting an environmental monitoring program is step one in standardizing the process, providing a guideline to minimize contamination risk and reduce the possibility of recall. Start by doing a risk assessment of your facility. It should include the plant layout, equipment, processes, and implementation plan. Identify areas that are typically prone to contamination, such as food contact surfaces, drain locations, and employee touch-points as prioritized zones for sampling.

Typically, environmental monitoring programs target Listeria species (L. spp.) rather than Listeria monocytogenes (L. mono), because L. spp. is an indicator that pathogenic strains are able to grow. Therefore, eradicating L. spp. essentially also eliminates L. mono.

The FDA recommends seven elements of a plan in order for it to be effective. The program should:

  1. Be scientifically valid;
  2. Specify whether you are testing for L. spp. or L. mono;
  3. Identify the locations from which samples will be collected and the number of sites to be tested during routine environmental monitoring;
  4. Identify the timing and frequency for collecting and testing samples;
  5. Identify the test(s) conducted, including the analytical method(s) used to test for Listeria;
  6. Identify the laboratory you are using for conducting testing; and
  7. Include corrective action procedures you will use when Listeria is found.

Of course, location and timing should be risk-based and can differ between plants that produce raw products intended to be cooked and RTE products, for example. It should also be noted that this risk analysis may identify other tests to be performed on the environment. This is beyond the scope of this article, but should nevertheless be considered. The number and location of sampling sites and the timing and frequency for collecting and testing samples should be adequate to determine whether Listeria control measures are effective. The FDA suggests including at least five food-contact surfaces and five non-food-contact surfaces in the environmental monitoring program for ready-to-eat (RTE) foods. These are the minimum numbers of samples. Sites should be representative of the facility. In cases of large plants, more surfaces may need to be monitored.

In terms of timing, the most important time to collect environmental samples is several hours into production or just before cleanup. Taking samples too close to the time that surfaces have been sanitized may interfere with the testing and give an inaccurate depiction of contamination. Collect samples at least monthly, or increase frequency for higher-risk foods such as RTE foods that support the growth of Listeria. For higher-risk conditions, consider weekly sampling.

In general, the environmental monitoring program should be developed and implemented with consideration for the level of risk of the product and risk associated with the facility and equipment. At the start of a new environmental monitoring program, conduct a deep clean of equipment and facility before conducting a baseline swabbing.

The Program in Practice

To get the most out of your environmental monitoring program, team support is essential. Dedicate a crew that is trained in chemical use and sanitation to conduct the sample collection and documentation. This not only establishes a system of accountability for collecting samples and reporting results, but it also creates a team that has a full focus on identifying potential contamination. As part of training employees, it is important that swabs be taken as consistently as possible to ensure an “apples-to-apples” comparison day-to-day. This even includes how much pressure is put on the swabs and exact locations swabbed. This will allow for meaningful data trending over time.

Determine what will be done to correct a positive Listeria finding prior to starting the program. This will ensure a smooth process for getting business up and running quickly in the inevitable event of contamination. With the prevalence of Listeria, it is likely you will have several positive results from various locations in the testing program. However, quick identification and an effective process for remediation are key to limiting disruption.

It can also be very helpful to set up a data reporting system to identify trends or “hot spots” where contamination is repeatedly found. This will help you reevaluate where your sanitation focus should be, as well as suggest more frequent sampling if a particular area is problematic. From there, you can reroute employee traffic patterns; clean, repair or replace equipment; and work to limit the introduction of Listeria from the outside environment.

Working With a Trusted Testing Lab

As you begin your environmental monitoring for Listeria, consider the laboratory that you’ll choose to conduct the testing. When you work with Barrow-Agee Laboratories for microbiology testing, you receive the benefit of our ISO 17025:2017 scope of accreditation and our proficiency testing scheme for microbiology, providing assurance that you’re working with a proven and accountable testing partner.

Contact us to learn more about our microbiology testing services.

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Barrow-Agee Laboratories Staff
Barrow-Agee Laboratories is a laboratory testing services provider for numerous industries that support consumers and businesses alike. Whatever your testing needs may be, Barrow-Agee has the testing solution and support to help you get the results you need.