In the past 25 years, there has been a great evolution in the food and feed manufacturing industries, from a reliance on finished product testing, to intensive environmental monitoring programs (EMPs). These programs can take many forms, ranging from very generic indicator monitoring (testing for ATP or aerobic plate counts), to specific pathogen EMPs, with the most common being Listeria spp. and Salmonella—organisms that are uniquely qualified to take up residence in food manufacturing plants. While these programs can look very different, they all generate data that can be used to improve food safety protocols.
Most EMPs that look for broad indicator groups are quantitative. With ATP testing, most detection platforms provide quantitative data in the form of relative light units. If using aerobic plate count data, this too is quantitative, yielding counts typically reported as colony forming units per sample. Other quantitative indicator groups used in EMPs include yeast and mold, coliforms, and Enterobacterieacea. Over time, statistical process controls can be used to determine when counts are trending upward or when there is a sharp spike in counts from the established baseline data, indicating a potential problem.
In contrast, most pathogen EMPs are based on qualitative testing. In other words, results are reported as either positive or negative. One of the limitations of this type of testing is that it is unknown whether there was a single cell present on the sample, or if there were thousands, as both can result in a positive result.
Getting Complicated
EMPs have gotten much bigger and more complicated, often testing for multiple pathogens in multiple areas of a facility. For example, in the early days of Listeria EMPs, many programs sampled only drains in the ready-to-eat (RTE) area. If a drain was positive, it was re-sanitized and re-tested. Today, it is not uncommon for a food or pet food manufacturing facility to test for quantitative indicator groups at pre-op to verify the effectiveness of sanitation (mainly on product contact surfaces), and also test for specific pathogens in multiple sampling zones (see Figure 1) and in multiple hygienic zones of the facility (see Figure 2). This increasing complexity of EMPs also means that the data evaluation becomes more complex.
In addition to these complexities, EMP data can come from several different types of testing. Routine monitoring is the backbone of most programs. It is the daily, weekly, or monthly testing that is conducted in a relatively steady manner to verify the efficacy of multiple prerequisite programs, such as sanitation, employee practices, hygienic design, and hygienic zoning. Quarterly sampling is not recommended since the time between testing is too great should a positive be found and a corrective action implemented. If the routine monitoring indicates that there is a problem, another form of testing kicks in, the investigational sampling. This testing is conducted to try to find the root cause or origination of the contamination. Investigations can be completed with just a few samples, but more realistically, hundreds or thousands of samples may need to be processed to solve a pathogen contamination issue. Another type of testing that can generate valuable data is special cause sampling. This includes the “extra” testing that is done to help verify control during unusual events, such as construction projects, inclement weather, power interruptions, or even periods of unusually high production volumes.
Testing Positive
It is now nearly universally acknowledged that a good EMP will sometimes generate positive results and should be viewed as a win/win situation. Most regulators and auditors understand this, and the focus of their attention often becomes the appropriateness of the investigation and the corrective actions. This is where a good data management system is especially critical. The first important component of an investigation is understanding what should trigger an investigation. With a quantitative program, it may be triggered when a gradual but real increase in counts has occurred or when a spike above the usual background level occurs. For a qualitative pathogen EMP, the trigger may be a single positive on a Zone 1 site (direct product contact), or a repeat positive in this same area. It could also be a general increase in the number of positives in an area or zone.
Once an investigation has been triggered, a multidisciplinary team (probably the same team that devised the routine monitoring program) should meet and discuss what is known and what is unknown about the issue. This team should include members who can inject critical viewpoints in the investigation, often experts from production, sanitation, quality assurance, maintenance, engineering, or any other areas that might contribute to the investigation. This team should interview other employees and check records to determine if any unusual events happened before or during the contamination event. For example, were there any unusual moisture events, such as a roof leak, power failure, construction, formulation or process change, etc.? Answering these types of questions often leads to multiple theories that need to be followed up with additional testing and fact finding.
As EMPs began to mature, many groups found that mapping is a critical part of data management. Being able to visualize which sites have been sampled and which have tested positive or negative is extremely valuable in helping to solve contamination issues and continuously improve the EMP. Mapping can range from a simple drawing pinned on the wall with multiple Magic Markers to indicate positive and negative findings, to sophisticated computer programs (see Figure 3). A map will typically show two dimensions, but it is also important to somehow capture the dimension of time. Being able to look back over a year’s worth of data to see if certain areas or related practices are linked to a higher occurrence of positives can help pinpoint problems. It is also important to have historical references. Many facilities unfortunately have high turnover of personnel. Having maps and other documentation to help illuminate past issues, investigations, and corrective actions can be important to prevent history from repeating itself.
Every environmental positive is not created equal. The reaction to a positive in a Zone 3 drain, far away from exposed RTE product will be much different from the reaction to a Zone 1 product contact positive. The EMP team needs to have a system that knows when to initiate and escalate the investigation and corrective action activities commensurate with the risk implied by the positive sample finding(s). Being able to visualize a series of positives in relation to the physical layout of the facility, process flow, and employee activities can greatly aid in informing the direction of the investigation and corrective actions and help keep the pathogen out of the finished product. The concept of “seek and destroy” means that the EMP teams seek out the target in the most likely places, sampling areas that are difficult to clean and sanitize (and therefore also difficult to reach for sampling). This often involves very complete and careful disassembly of complex equipment while sampling each part. Then the team destroys the target organism or growth niche by seeking the root cause, implementing a permanent fix, and then verifying that the issue truly has been permanently eradicated.
Sharing EMP data between similar facilities has played an important role in helping facilities improve their EMPs. Some of the earliest data sharing efforts were between facilities owned by the same company. It then expanded to supplier groups, meeting at a common customer, and then various trade associations. Understanding where similar facilities have found environmental pathogen problem areas have allowed EMPs to greatly accelerate their effectiveness.
Another important tool in environmental pathogen investigations is the use of strain tracking. One of the earliest examples of strain tracking was the use of serogroup or serotype data to track individual strains of Salmonella. Today we can differentiate to an even higher degree using methods such as ribotyping or whole genome sequencing to differentiate between closely related targets. The ability to determine whether a facility has a house pet (an environmental pathogen that is well-adapted to the facility conditions and is isolated routinely and over long periods of time) or house pests (transient strains that are introduced from outside the facility and are then eliminated) can be key. Regulators that find repeat occurrences of a house pet may determine that the facility is operating under insanitary conditions, with very serious consequences to continuing operation of that facility. Many companies are incorporating strain tracking into their EMPs to understand persistence and better protect public health.
Improving Protocols
During investigations and corrective actions, it has often been found that the process flow has contributed to a contamination issue. For example, mapping may indicate that a higher level of Salmonella positives has been found on the floor in the hallway leading to a trash compactor. After further investigation, it is found that there is moisture from rain events that is entering the trash compactor, causing growth of Salmonella. Steps in improving this situation include, better staging of garbage, having special footwear dedicated to the area, and applying a dry floor sanitizer powder. A more permanent fix can then be worked on, going to the root cause, and fixing the problem with the ingress of moisture into the area.
Sanitation is another key prerequisite program that can be improved based on the results of EMPs. If elevated levels of indicators are found during pre-op sampling, the sanitation practices can be changed to fix the problem. Examples include retraining of personnel, changing types or concentrations of detergents or sanitizers, modifying water conditions (hardness), changing water pressure or temperature, or increasing the frequency of sanitation. These same changes can also be implemented in response to finding pathogens in a pathogen EMP.
Hygienic design improvements can be made (and the capital expense justified) by the EMP results. Equipment design has been greatly improved as industries have identified growth niches or harborage points within equipment. Elimination of difficult-to-clean areas, such as hollow support structures, hollow conveyor rollers, door gasket material, conduits, poorly sealed control panels, etc., have helped eliminate environmental pathogen problems, and have secondary benefits, such as reduced spoilage issues and more efficient cleaning and sanitation. Designing equipment with integrated clean-in-place sanitation systems, or access points that can be reached without the use of special tools, has also led to great improvements. In addition to equipment, the facility itself can be improved through better hygienic zoning, air flow changes, and the prevention of moisture or pests, etc.
Results of EMPs have also led to changes in products being produced. Changing products at high risk for environmental pathogen issues to those at low risk can be the most bulletproof way to reduce the overall public health risk. For example, the reformulation of RTE meat and poultry products with listeriostatic antimicrobials, such as lactate and diacetate, has moved many of these products into a lower risk status by preventing the growth of Listeria during shelf life.
Finally, the EMP itself can be improved based on the EMP results. In fact, EMPs should always evolve as our knowledge about the pathogen, product, process, and facility evolve. When an EMP, process, product, or facility is new, the EMP needs to be rather extensive because the EMP team will be exploring, looking for where potential problem areas might be. With the collection of months’ or years’ worth of data, the EMP can be fine-tuned, moving from reactionary to preventive. Often this means that individual samples can be better optimized to give the most value. Positives should become very rare, and when found, they are welcomed as a way to improve the system.
Dr. Freier is vice president for scientific affairs, microbiology, at Mérieux NutriSciences and has published several refereed journal articles, book chapters, and patents, and given numerous presentations on various food safety-related topics. Reach him at [email protected].
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