Biological indicators are test systems that contain viable microorganisms with a defined resistance to a specific sterilization process. They help monitor whether the necessary conditions were met to kill a specified number of microorganisms for a given sterilization process.
Bacterial spores are some of the toughest microorganisms to kill. Since Geobacillus stearothermophilus spores demonstrate a high resistance toward steam and vaporized hydrogen peroxide, they’re used in biological indicators that monitor these sterilization processes, while BIs with Bacillus atrophaeus are used for ethylene oxide (EO) and dry heat applications.
A passing result for the BI demonstrates that the sterilizer is effective in killing a large number of highly resistant bacterial spores, providing users with a level of assurance in their sterilization process.
– ISO 11135
– ISO 11138
The Biological Indicator Population Verification test determines the initial number of spores on a biological indicator (BI).
This test is used to:
• Verify the BI manufacturer’s labelled population.
• Enumerate survivors from a sterilization process to determine lethality rates and D-values.
Initial population verification is can be performed as a quality control because the population of the BIs can change during shipping and/or storage. As specified by the ISO 11138 standard, the initial population of microorganisms shall be higher than 10⁶ CFU/BI.
Population enumeration on samples exposed to the sterilant is also important because it provides quantitative data whereas a BI sterility test only provides growth/no growth results.
At Abiolabs, we have the capability to perform testing on all types of biological indicator configurations such as BI strips, discs, stainless steel sutures, inoculated wires, and spore suspensions.
Biological Indicators (BIs) are widely used to monitor the efficacy of sterilization processes. BIs provide a high level of sterility assurance and are ideal monitors of the sterilization process.
The BI Sterility test is performed on exposed BIs after completion of a sterilization load through either a validation or routine lot release monitoring. The test is qualitative and the result is expressed either as growth or no growth of the appropriate indicator organism.
The test is performed on BIs subjected to different types of sterilization such as ethylene oxide, steam, dry heat, vapour phase hydrogen peroxide and ozone, as well as other processes. Both traditional BIs and self-contained BIs may be tested. This test is typically performed during validation as well as during routine production as a lot release test.