Environmental Monitoring in Microbiological Labs

results are out of specification, cleaning/sanitation procedures should be reviewed and revised. When areas such as door handles, carts, pipettor handles, or control panels are swabbed between cleaning and sanitation, the results can be used to provide an indication of not only their current microbial load, but how often the sites should be cleaned/sanitized. In this regard, close monitoring, or tracking, of data is a key function of environmental monitoring programs. APC, coliforms, and Enterobacteriaceae are examples of indicator organisms.

One note about indicator samples is they may be tested to assess cleaning/sanitation efficacy on a more frequent basis or at specific times.

Air monitoring. Just as in a production environment, laboratory air quality can be monitored when yeast and mold is tested. Mold spores, in particular, can be spread via air

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Table 2: Sampling frequency for zones and organisms.

currents. Many times, yeast and mold counts have seasonal variations. Summer months may show higher counts than winter, especially in states that experience winter freezes. Increased counts may also indicate water leaks, clogged air filters or doors left open. There are a number of methods for monitoring air quality. The use of an air sampler that draws air and impacts it onto a petri dish is a valuable tool. Alternatively, passive air monitoring wherein settling plates are used is a common, inexpensive method of air collection—media is exposed to operational air for a pre-determined amount of time. During air monitoring, normal operations should be taking place.

Sampling frequency. The frequency depends on the number of sites and how often the lab wants each site sampled. For most labs, at least weekly sampling is a good place to start. Sampling should take place on different days of the week to account for differing sample loads and activities. Table 2 outlines an example of a sampling frequency program. When samples are selected, they should be randomized by using a random number generator such that all sites have an equal chance of selection. Keep in mind that with randomized sampling, some samples may be tested two or more times and some may not be tested at all in a given timeframe.

Setting specifications. For any program, setting specifications is not an exact science. Zone 1 post-sanitation results should be less than 10 colony-forming unit/sponge or negative depending on the type of assay. Zone 2 and 3 specifications may be set initially and then change depending on baseline data that is collected over multiple months. Tracking and trending consecutive data from six to 12 months is a good rule-of-thumb to set specifications. After this period of time, the lab management reassesses and possibly revises specifications. Table 3 provides examples of specifications for zones 1 to 3.

Data collection and review. Each month, the site list and results should be reviewed by lab management to ensure sampling is conducted as per the SOP, that out-of-specification results have been addressed, and that corrective actions were effective and verified. This review also allows identification of developing trends. All data should be reviewed in a historical context and relevant corrective/preventive actions should be included in the monthly review.

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Table 3: Specifications for microorganisms
for zones 1-3.

Corrective actions. If presumptive and/or out-of-specification results are observed, involvement of varied management levels provides a diversity of perspectives and ideas for corrective activities.

Corrective actions are activities that are conducted as soon as possible after result notification. For example, the sample site and surrounding area will be cleaned and sanitized before the close of business on the day the results are observed. After cleaning and sanitizing, the sample site(s) are to be sampled to verify the efficacy of the cleaning/sanitizing event. Sampling of the site will continue each day until three consecutive in-specification results are obtained. When this qualification is met, the sample is returned to the site list for routine monitoring. These samples are to be taken after cleaning and sanitation of the site has been performed. If any of these samples are out-of-specification an investigation should be launched.