ASP Sterrad Velocity Reader - Page 35

Operation 4
STERRAD VELOCITY Reader User’s Guide 29
9 Note: The STERRAD VELOCITY Reader can detect residual enzyme activity even
when the G. stearothermophilus spores are damaged to the point they will not
grow. Therefore, a BI may read as uorescence-positive even when it is visually
growth-negative. This characteristic of the enzyme response provides an increased
margin of safety and meets the criteria of the FDA reduced incubation time protocol
(greater than 97% correlation between BIs that are growth-positive at 5-7 days
post-sterilization and BIs that are read as uorescence-positive at 15 minutes).
Check the CI, on the top of the cap, for color change from red/pink to yellow to
conrm that the BI has been exposed to hydrogen peroxide. Incubate the test BI and a
positive control at 55–60°C (131–140°F) for 5 to 7 days. After incubation, inspect the
growth medium in the processed BI for color change from purple to yellow. Compare the
processed BI with the positive control and record results.
9 Note: For easier color comparison, observe the BIs against a white background.
The absence of a color change of the growth medium in the processed BI (i.e.
the growth medium remains purple as compared to an unprocessed uncrushed BI)
indicates that a sterilization condition was achieved (sufcient to kill at least one
million of the most resistant identied bacterial spores in the BI).
Color change from purple to yellow of the growth medium in the processed BI
(as compared to the positive control BI) indicates that a sterilization condition was
not achieved.