CDC Guidelines for Sterilizer Spore Testing

Biological monitoring—commonly known as spore testing—is a critical step in verifying the effectiveness of sterilizers in medical, dental, and laboratory environments. According to the Centers for Disease Control and Prevention (CDC), weekly biological monitoring is the minimum recommended standard to ensure that sterilization processes are functioning correctly.

Spore testing uses biological indicators (BIs) that contain highly resistant microorganisms such as Geobacillus or Bacillus species. A negative result means the sterilization cycle has effectively killed these organisms, indicating that other, less-resistant microbes have also been destroyed.

Key CDC Recommendations for Spore Testing:

  • Frequency: Perform biological spore testing at least weekly, or more frequently if the sterilizer is heavily used.
  • Implantable Devices: Test every load containing implantable items. Ideally, do not use the items until a negative test result is confirmed.
  • BI Placement: Follow the sterilizer manufacturer’s instructions for placing the biological indicator in the most challenging location of the load.
  • Control Indicator: Always use and incubate a control BI (unprocessed) to verify that spores are viable prior to sterilization.
  • Positive Spore Test:
    • Immediately remove the sterilizer from service
    • Quarantine any items processed since the last negative test
    • Repeat testing to confirm the result
    • If the repeat test is negative and procedures were correct, you may return the sterilizer to service
    • If the repeat is still positive, inspect or repair the sterilizer before resuming use
  • Recordkeeping: Maintain detailed logs of all spore test results and corrective actions.

Additional Monitoring Practices Recommended by the CDC:

  • Mechanical Monitoring: Review and document sterilizer cycle parameters (e.g., time, temperature, pressure) for each load.
  • Chemical Monitoring: Use chemical indicators (e.g., color-changing strips) to confirm that the sterilizing agent has reached the instruments.

Important: While mechanical and chemical indicators can help identify malfunctions, biological indicators remain the most reliable method for verifying sterilization.

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Disclaimer:

This content is provided for general informational purposes only. Please visit the official CDC website for the most up-to-date and authoritative infection control guidelines.

https://www.cdc.gov/infection-control/hcp/disinfection-and-sterilization/index.html

https://www.cdc.gov/infection-control/media/pdfs/Guideline-Disinfection-H.pdf