We use cookies to understand how you use our site and to improve your experience. This includes personalizing content and advertising. By continuing to use our site, you accept our use of cookies. View our Privacy Statement.

Geobacillus Stearothermophilus: Say It Five Times Fast

11.23.2022 • Industry News

Not only is it difficult to say, it’s difficult to kill. If you’ve ever wondered what is in the biological indicator (BI) vial used in the sterilizer for load validation, it’s a spore of the organism called Geobacillus stearothermophilus. To validate successful sterilization, we need to test against (and kill) the most extreme organism…Geobacillus stearothermophilus.

Geobacillus stearothermophilus was first discovered in the 1920’s and the word “geo” means “soil or earth” as it’s commonly found in soil, hot springs, and ocean sediment. Geobacillus stearothermophilus is one of the most heat-resistant organisms known and when we achieve total destruction of this spore through the sterilization process, we know that we’ve destroyed all other microorganisms that may be present along with it. The BIs we use in sterilizers are designed to represent worst-case microbial bioburden (number of viable microorganisms present) on a surgical instrument. The cycle parameters we use for steam sterilization are based on the time and temperature required to inactivate Geobacillus stearothermophilus spores. Many of the spore strains of Geobacillus stearothermophilus in BI vials are fluorescent-tagged. If viable spores are present post-sterilization, the fluorescent compound is detected during the incubation period and a positive result is displayed.

For steam sterilization, AAMI/ANSI ST79 recommends monitoring the sterilization loads through the use of BIs. The standard states, “BIs should be used within process challenge devices (PCDs) for routine sterilizer efficacy monitoring at least weekly, but preferably every day that the sterilizer is in use. BIs within a PCD may be used as part of the criteria for release of loads. Additionally, BIs with Type 5 integrating indicators within PCDs should be used to monitor every load containing implants; implants should be quarantined until the results of the BI testing are available. If a PCD containing only a BI is used to release a load, the load should be quarantined until the result of the BI is known.”

What do you do if you have a positive read-out? Have a policy in place. Action needs to be taken right away. The following points from AAMI/ANSI ST79 13.6.4 will help you get started on creating a formalized policy:
  • The department head or designee should be notified
  • If overloading is suspected, the sterilizer should be reloaded, and the cycle rerun
  • After examination, if the malfunction cannot be corrected immediately, the cycle should be terminated in accordance with the sterilizer manufacturer’s written IFU
  • The load should be considered nonsterile, and the sterilizer should be removed from service
  • The load should be removed from the sterilizer and quarantined so that it is not inadvertently released for use
  • The hospital engineer or maintenance contract service should then be notified, the root cause should be identified, and the sterilization process failure should be corrected
  • The same investigative procedure should be followed at the completion of the cycle if the physical monitors, external CIs, or the monitor in a PCD (BI challenge test pack or CI challenge test pack) indicates a questionable cycle
TECH Talk Tip: Ask why! Why do we do what we do every day? Explore the reasons why the standards and recommended practices were created and written. The questions we ask enhance our knowledge of our day to day practices and elevate the standards of how we perform in our departments. To obtain a copy of the standards visit AAMI.org.

Jamie Zarembinski, CCSVP
Senior Sales Representative - Clinical Educator
Key Surgical