When selecting a biological indicator (BI), there are a lot of things to consider, but the three most important considerations are below:
1. What Type of Sterilization Is It?
Sterilization processes vary from chemicals to extreme temperatures to plasma infused chambers. These processes are all detrimental to the survival of biological materials but the selection of what particular biological indicator to use for each individual process is of extreme importance.
Biological indicators are made up of bacterial spores presented on or within some form of carrier which can vary depending on the specific application. The spores themselves have been selected for a particular process due to their inherent resistance. Geobacillus stearothermophilus is the ideal species to select for Steam and H202, Bacillus atrophaeus is appropriate for monitoring Ethylene Oxide and Dry Heat sterilization and Bacillus pumilus spores have shown specific resistance to gamma irradiation sterilization processes.
2. What Product Is Being Sterilized?
A cold, 2 Liter flask of water would take much longer to reach sterilization temperatures than a 100 ml flask of water in a steam sterilizer. Similarly, the products that are introduced to the sterilization cycle can have a dramatic effect on the sterilizer’s ability to effectively deliver lethal insult. Is the product a solid or a liquid? If solid, it is porous? What is the position within the pack/product that will be the most difficult spot to achieve sterilization conditions? All of this information is useful when discussing proper BI placement and selection.
3. Does Your Facility Have the Necessary Microbiological Expertise?
Many facilities do not have a laminar flow hood or similar equipment necessary for performing an aseptic transfer which is required for a number of biological indicators. Self-contained (SCBIs) products are available that do not require this type of equipment but traditional spore strips require this type of transfer prior to incubation. It is important to consider this distinction when determining what BI is proper for your intended use.
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