The Evolution of Biological Indicator Systems

A decade ago, biological indicators (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 sterilization failures.

In recent years, the time to read for BIs drastically improved with the introduction of fluorescence readout. Today, the STERRAD VELOCITY™ System* offers the quickest turnaround time for a Biological Indicator/Process Challenge Device (BI/PCD) with a readout time of 15 minutes**.

Rapid Readout Technology – 15 Minutes** Time to Results

STERRAD VELOCITY™ Biological Indicator (BI)/Process Challenge Device (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. 

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 and improve record keeping. Via ASP ACCESS™ Technology, the STERRAD VELOCITY™ Reader integrates with STERRAD™ Sterilizers to reduce the potential for human errors with automatically correlated sterilizer and BI records 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.

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

*Fastest BI/PCD currently marketed for STERRAD™ Sterilization Systems.

**15 or 30 minutes to results dependent on software version of the STERRAD VELOCITY™. Refer to the IFU for actual time to results. Fastest BI/PCD currently marketed for STERRAD™ Sterilization Systems.

Meet the Author

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

Sophia Czechowicz Ph.D.

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