Biological Indicators
Indices of life for gravity steam cycles at 270°F/132°C. An isolated biological indicator (BI) for 270°F/132°C gravity steam cycles is comprised of a Geobacillus stearothermophilus spore strip, a glass ampule that is sealed and contains growth medium and a bromocresol purple pH indicator dye system, a blue color-coded cap that has holes for sterilant penetration and a filter that acts as a bacterial barrier, and a chemical indicator on the label that turns brown after processing. To combine the processed spore strip with the growing media, the vial is "crushed" after sterilization.
