Biological indicators are required to confirm that a sterilisation or decontamination process has been adequately performed. Biological indicators are often referred to as BI’s and are defined by ISO, AAMI or ANSI standards.
A BI is a test that is typically provided in a paper wrap or vial to enable easy application into a process. These tests contain viable microorganisms providing a very defined resistance to specific steam or chemical sterilisation processes. The biological indicator provides information to the user on whether the necessary conditions were achieved within sterilisation process to kill the specified number of microorganisms within the BI thus providing confidence that the process is working correctly and working within specification.
Endospores, or bacterial spores, are the microorganisms that are primarily used in BI’s as they are considered some of the most robust microorganisms to kill. It is worth knowing that additionally, bacterial spores are chosen for a specific sterilization process based on their known resistance to that particular process. For example, Geobacillus stearothermophilus spores are used in BI’s that monitor steam and vaporised hydrogen peroxide as they possess a high degree of resistance towards these sterilisation medias.