Components in a Pathogen Environmental Monitoring Program

When developing a sampling plan for Salmonella, target warm (non-refrigerated) areas exposed to moisture (roof leaks, condensation, over-spray from cleaning, etc.), and product residue. Sampling sites are typically concentrated in areas near food contact surfaces and other areas in the primary Salmonella control area (PSCA), the area between the kill step and final packaging. In contrast to Listeria, Salmonella growth niches do not typically occur on product contact surfaces due to the dry nature of the product and the self-cleaning or scouring nature of the dry product passing over the contact surfaces. The Salmonella PEMP sampling plan should concentrate on non-product contact surfaces in the PSCA.

In addition to the samples scheduled to be taken based on the sampling plan, technicians should be allowed to take “creative” samples, investigating novel sites not sampled in the past. Technicians need to be trained to understand the difference in the implication to finished product between sampling a product contact surface and a non-product contact surface. Typically, if a pathogen such as Salmonella is found on a product contact surface, the product contacting that surface would be deemed to be adulterated and may need to be recalled if the product had not been placed on hold.

The goal of the PEMP is to find the intended target. Technicians doing the sampling should be incentivized to find positives. This is counterintuitive to many people. While the overall food safety goal is to maintain critical processing areas free of the pathogen or indicator group, the goal of the PEMP is to find these organisms. In the U.S. RTE meat and poultry industry, this mentality is known as “Seek and Destroy,” and the diligent search for the target needs to become part of the food safety culture of the facility.

Investigational sampling in response to a positive routine finding should be conducted with the goal of finding the true root cause of the contamination. The stringency of the investigational sampling will depend on the circumstances of the finding. Finding the root cause of a contamination issue is often very difficult and can require intensive disassembly and sampling of equipment and the environment. This investigation can continue for several weeks and involve taking hundreds or even thousands of samples. As part of the investigation, the food safety team also needs to consider changes or disruptions to normal production such as improper employee practices, drain backups, flooding, contractor work, power outages, etc., in addition to evaluating the test results.

Special circumstance sampling may be initiated even without finding positives during routine sampling. This can include taking extra samples during non-routine events such as facility construction, installation of new equipment, power failure, roof leaks, kill-step failures, or any circumstance that might lead to enhanced risk of contamination of the final product.

Sampling Methods

The next component of the PEMP should provide details about how samples will be collected, the type of sampling device to be used (e. g., sterile sponges with sterile gloves), the type of diluent to be used, and how the samples will be stored and transferred to the lab and tested. Typically, large areas should be sampled (greater than 1 square foot) using an abrasive sampling device, such as a microcellulose sponge wetted with a diluent like peptone water or a neutralizing buffer (if residual sanitizer might be present in the area being sampled). Samples should be refrigerated, not frozen, and processed by the laboratory within three days. Technicians taking samples should be trained in proper aseptic sampling procedures. Sampling should typically be conducted by starting in the cleanest area of the plant and ending with the dirtiest area to prevent inadvertent cross-contamination of the facility. Only methods validated for use with environmental samples should be used (AOAC International or rigorous internal validation). Testing should be conducted at a competent lab with appropriate quality control practices in place. The time from test initiation to result (turnaround time) is often thought to be less critical for PEMP than for finished product testing, as product is not typically placed on hold. However, quick turnaround time can be critical during an investigation. Similar to a crime investigation, clues are most helpful when the trail is still fresh.

Evaluation of Results

The final critical components of a PEMP are the evaluation of the results of the sampling and corrective actions prompted by those results. The results should be reviewed on a timely basis. Positive findings should be reviewed by the facility food safety team. Results should be organized in a manner allowing easy visualization of findings. The use of data spreadsheets and facility maps indicating positive and negative findings is recommended. When routine and/or investigational and/or special circumstance sampling indicates a problem, timely and effective corrective action must be taken. This activity should target the root cause of the contamination. Most effective corrective actions will involve more than simply re-cleaning or re-sanitizing the problem area. The food safety team should also consider changes in personnel practices, training, equipment or facility modifications, process or product changes, or other activities resulting in a permanent fix of the problem. Additional testing may be necessary to verify the adequacy of the corrective actions. All activities involving the PEMP should be documented.