The Evolution of Biological Indicator Systems

A decade ago, biological indicator (BIs) used a visual readout method to determine if a sterilization cycle successfully inactivated microorganisms. Because these antiquated BIs took one to seven days for growth readout results, they were an untimely indicator of potential catastrophic sterilization failures.

In recent years, the time to read for BIs drastically improved with the introduction of fluorescence readout. Today, the fastest time to results in the market is the STERRAD VELOCITY™ System with a 15-minute* readout.

Rapid Readout Technology – 15 Minutes* Time to Results

STERRAD VELOCITY™ BI/PCD contains two important components required for fluorescence readout:

  • α-MUG: a fluorogenic dye that becomes fluorescent upon enzymatic reaction with α-glucosidase (AG)
  • α-glucosidase (AG): an enzyme naturally produced by spores
velocity bi details

When the STERRAD VELOCITY™ BI/PCD ampule is crushed, the surviving microorganisms containing α-glucosidase (AG) are mixed with media that contains α-MUG. The enzymatic reaction splits α-MUG to 4-MU, a fluorescent compound, and Glucose.


If organisms survive after the sterilization cycle, the media will fluoresce, indicating a positive result. Conversely, if there are no surviving microorganisms after the sterilization cycle, the media will not fluoresce, and the BI is considered negative.

This advancement in technology enables sterile processing leaders to establish better balance between keeping up with clinical demand and confidence of BI/PCD results before releasing instruments. Fast time-to-read increases throughput for the busiest sterile processing departments and operating room.

Automated Record-Keeping Technology for Real-Time Audit Records

In addition to sophisticated rapid-read technology, STERRAD VELOCITY™ Biological Indicator System also has a unique connection to STERRAD™ Systems via ASP ACCESS™ Technology to enhance compliance through BI reminders per hospital policy, greater adherence to device IFUs, and improved record keeping. Via ASP ACCESS™ Technology, the STERRAD VELOCITY™ Reader integrates with STERRAD™ Sterilizers to provide a guided, error-resistant workflow with automatically correlated sterilizer and BI record to ensure consistent and complete BI records that are AAMI compliant. This provides the confidence in audit-ready BI records so that the focus is on protecting patients.

Learn more about ANSI/AAMI standards for low-temperature sterilization: Importance of Following Industry Standards and Guidelines

For more information on STERRAD VELOCITY™ BI/PCD rapid-read technology or automated recording-keeping ability, get a consultation from a sterilization expert.

*15 or 30 minutes dependent on software version. Refer to the IFU for actual time to results.

Meet the Author

Sophia Czechowicz Associate Director, R&D – Technical Business Solutions

Sophia Czechowicz Ph.D.

Associate Director, R&D – Technical Business Solutions, ASP