Environmental Monitoring in Microbiological Labs

It does not seem right that food production plants work so hard taking multiple samples of various types of surfaces, at all times of the day, looking to verify the efficacy of good manufacturing practices and sanitation protocols. The laboratory appears to have the easy part, just testing the samples, seemingly unaware of the how slow the hours pass waiting for results, the relief when they are in-specification, or the panic when they are not. It must be nice to be a laboratory! Well, not so fast. Lab personnel work through the same processes for the same reasons because similar protocols are followed. Laboratories will often

carry out environmental testing to ask: Are the good laboratory practices (GLPs) followed by the lab staff and management effective? Are the cleaning and sanitation practices effective? Has there been cross-contamination within the laboratory?

The laboratory environmental monitoring programs (EMP), as in a plant, will vary according to the predominant assays performed, lab areas, traffic patterns, air flow, equipment conditions, and even the season. Careful consideration is made in the development of the program so that it meets the needs of the individual laboratory, while covering the key components that every lab should follow. As those in a food production environment will see, an EMP followed by an in-house or a third-party contract lab adhere to similar steps to ensure that the data generated are accurate, reproducible, and dependable.

Key Components

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Table 1: Environmental zones for monitoring in a microbiological testing lab.

Environmental monitoring zones and site list selection. In any EMP, it is critical to define what constitutes highest risk areas, such as sample contact areas (zone 1), to lower risk areas, such as floors and walls (zone 3). The importance of developing a thorough site list and establishing zones cannot be underestimated. Each lab area where samples are logged-in/staged, media prepared, dishes washed, samples incubated, assays conducted, plates read, and materials autoclaved must have locations represented within the environmental monitoring site list.

If the trending data suggests that some zone 3 sites have been identified as “hot spots,” then site lists should represent this zone in proportions related to the data. The site list should be reviewed on a periodic basis to account for added or removed equipment, new test methods, substantive construction or site modifications, and any facility issue.

Since each lab may have different processing areas, equipment, and utensils, site lists may be unique for each lab even if they are under the same ownership. However, the principle of including sites within each critical lab area, representing all zones, remains across all labs. Table 1 provides a general overview of environmental zones in a lab.

Assays selected. The assays selected for each sample are those that are conducted on samples. For example, if incoming lab samples are tested for Listeria spp., Salmonella, coliforms, E.coli, and coagulase-positive Staphylococcus then those are the assays to be included in an EMP. Whatever organisms are tested, the same methods that the lab is asked to run are to be used for the EMP. When yeast and mold are tested, see Air Monitoring section below.

Sampling modalities include swab, sponge, amplicon, and air sampling. Amplicon sampling withstanding, samples are either categorized as indicator or specific organism.

Indicator organisms are used to assess the overall microbial load of a sample site. Aerobic plate count (APC) measures the number of bacteria that grow aerobically. Results are obtained in 48 hours. An APC assay can assess the efficacy of cleaning and sanitization when sponges are taken immediately after the event. When the