As with all other elements of a food safety program, your performance is only as good as the work of the people who make it run. One of the most critical aspects of your environmental monitoring program is training the sampler. The success of your environmental monitoring program depends on obtaining samples taken using proper aseptic technique, are representative of the processing environment itself, and have been stored correctly in transit to the laboratory. Additionally, adequate vector swabbing as a follow-up to any positive sample results is an integral part of this training.
The First Step in Environmental Monitoring
First and foremost, samplers must use the proper hygienic technique when conducting environmental sampling. Hands must be washed and sanitized; then, samplers must put on sterile gloves, taking care to not touch any nonsterile surfaces before touching the swab. Remember, the only nonsterile surface the swab should contact is the sample surface itself! Between swabs, hands must be sanitized, and gloves changed. It is often helpful to have a second person accompany the sampler; they can assist with carrying supplies, recording sample sites, and staging the swabs (labeling, opening the sample bags).
How to Take a Sample
When sampling, work from the highest hygiene areas (zone 1-product contact sites) out to the lower hygiene areas (zones 2, 3, and 4). Also, be sure to wipe down zone 1 sites with the appropriate sanitizer after sampling. Check out the article The Benefits of Environmental Monitoring for details about zones. These measures will reduce the risk of the sampling team, causing any cross-contamination of this critical area.
Once you’ve taken the samples, they must be appropriately handled and transported to the laboratory promptly. Keeping the samples cool (< 45 F) prevents microbial growth; testing must be conducted within 48 hours to ensure that the organisms present have not died out. Samples should also include a negative control-this is a swab carefully removed from its bag and returned without being used. The negative sample checks a few things, sterility, integrity of the swab, and hygienic technique of the sampler.
The Importance of Environmental Monitoring
Beyond the immediate details of how to take a sample, it is critical for the environmental monitoring team to understand the importance of the program itself. This should include presentations on food safety, basic food microbiology and the culture of food safety. Having a thorough knowledge of the facility, the products, and its processes is critical: monitors must have the discretion to select and rotate the sites that they sample. Only by rotating the sampling sites will you obtain a comprehensive picture of the hygienic status of that zone.
Handling a Positive Result
This level of understanding is particularly crucial when responding to a positive pathogen result from an environmental sample. In essence, we must try to identify any harborage sites that might be the source of the contamination. If contamination is found, you must immediately quarantine the sample site and surrounding area to prevent further spread of contamination. The quarantine measures can range from cordoning off the area around a drain (zone 3) to halting production for a zone 1 product contact site and holding any affected product. The next step is intensive environmental sampling around the initial positive site to assess whether the contaminant has spread or was an isolated incident.
This type of sampling is commonly referred to as vector swabbing since we are attempting to follow the contaminant’s spread. When swabbing, use a bullseye or starburst pattern. With this technique, you can pull as many as 20 samples from the area around the positive site. With Zones 1 & 2, this can involve breaking down the processing equipment for sampling, followed by deep cleaning, sanitizing, and resampling to confirm effectiveness (the seek & destroy process). Zones 3 & 4 areas such as drains/floors may involve sampling traffic patterns, followed by cleaning a large area (50-foot radius or more around the site) and resampling. The area around the original positive site is typically resampled daily to assess the effectiveness of the control measures; 3 days in a row without another positive are considered a success.
Why Environmental Monitoring Matters
These activities and the test results they generate form key pieces of information for your root cause investigation into what caused the contamination, the corrective actions taken to resolve the incident, and the preventative measures developed to prevent its recurrence. Under FSMA, environmental monitoring programs and procedures must be scientifically valid and documented. You should train those involved in the program on an annual basis. It is critical that environmental monitoring samples be taken by personnel who do the job correctly and understand its significance-food safety is on the line!