Biological indicators provide the best assurance of sterility by challenging the sterilizer with quantifiable, highly resistant spores. Biological indicators are used for load control monitoring which is the process by which a load is monitored and released based on the result of a biological indicator (BI) in a test pack.

3M™ Attest™ 1261 Biological Indicators for 132°C (270°F) gravity steam

Self-contained BI for 132°C (270°F) gravity steam cycles consists of a Bacillus stearothermophilus spore strip; sealed glass ampule with growth medium and a bromocresol purple pH indicator dye system; blue color-coded cap with holes for sterilant penetration and a hydrophobic filter as a bacterial barrier; and a chemical indicator on the label that changes from rose to brown when processed. After sterilization, the vial is "crushed" to join the growth media with the processed spore strip. The BI is incubated for 24 hours for a visual color change readout. A color change to yellow indicates surviving spores and a positive result.