For decades, non-functional particle cleaning levels have been closely measured and monitored in pharmaceutical cleanrooms, in an effort to improve drug quality and save patient lives. In parallel effective microbial contamination levels have also been closely measured and monitored through the use of settle plates and subsequent identification of colony forming units.
The main risk to patient safety is widely considered to be functional particles, such as microbes that are able to replicate. The presence of a microbe may not pose a threat to the patient’s immune system, but a viable microbe must multiply under the right conditions and form a colony of microbes, leading to infection and illness in infected patients. Drug dosage.
Measuring and reporting viable particles presents its own challenges, not least of which is the delay between collecting viable particles on the settling plate and deciding whether colony-forming units are present or not. . Different species of microbes favor different environmental conditions for growth and replication. Some species favor lower temperature environments; Some prefer higher temperatures to stimulate growth. Even the acidity of the environment can have an effect, and samples that are incubated and declared clear of viable particles may later contain microbes that thrive upon exposure to pH changes.
A common factor that affects all microbes is the presence of water. Without water, microbes will not thrive and this presents an added challenge to the collection and incubation of microbes, i.e. nutrients on the settle plate dry out when exposed to the cleanroom and this can be a particular problem for active air samplers where the settle plate is exposed to a forced flow of drying air.