Checklist: Positive Biological Indicator in Steam Sterilization
Key Takeaways:
- A positive biological indicator (BI) result requires a comprehensive investigation, including review of sterilization cycle parameters, BI handling, equipment functionality and environmental conditions.
- BI placement, spore count and D-value must be appropriate for the application, and aseptic technique must be strictly followed during culturing to avoid false positives.
- Sterilizer performance should be verified, including condensate trap function, temperature distribution and air removal efficiency (e.g., via Bowie-Dick or leak tests).
- Environmental monitoring and equipment maintenance records (e.g., HEPA filters, incubators, clean benches) should be reviewed to rule out contamination sources.
- Repeat BI testing should only occur after corrective actions are taken, and the sterilizer should remain out of use until satisfactory results are confirmed and quality assurance guidelines are met.
Using biological indicators in the autoclave steam sterilization process helps validate that the conditions to kill microorganisms were met. The BI is exposed to the sterilization process and then incubated to determine whether any endospores survive. If no spores survive or grow, the test is a pass. A passing result demonstrates that the sterilizer is effective in killing a large number of highly resistant bacterial spores.
But what if the test is a fail? It could be caused by several factors, including operator experience, load preparation and sterilizer condition. When a positive culture results after processing the BI in a validated steam sterilization cycle, finding the cause is critical.
Download the BI Checklist to help discover the source of a failed biological indicator test result.
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