Biological Indicators

BIOLOGICAL INDICATORS FOR MICROORGANISM CONTROL

Biological Indicators are designed for the routine control of steam sterilization processes (vacuum-assisted or gravity air displacement) and allow verification of the autoclave’s reliability in accordance with international systematic control requirements. Each tube contains Geobacillus stearothermophilus spores (ATCC 7953) on a carrier and a culture medium that changes color after incubation: if the process was ineffective, the medium changes from purple to yellow (growth); if effective, it remains purple (no growth). Final reading after 24 h incubation at 58–62 °C. Single-use product, hermetically sealed, with lot number and expiry date on each vial.

HOW DO THEY WORK? (color interpretation)

• Purple → Yellow: bacterial growth ⇒ sterilization failure.
• No change (remains purple): correct sterilization.
• Check color at intervals during incubation; final reading after 24 h (58–62 °C). 
   

INSTRUCTIONS FOR USE

• Complete the indicator label.
• Remove the tube; check the internal glass ampoule. Place it at the center of the load / near the autoclave door.
• Sterilize with the usual cycle.
• At the end, wait ≥ 5 min, remove with gloves and goggles, allow to cool.
• Verify that the chemical indicator on the tube has turned black (exposure to ≥ 121 °C).
• Break the internal ampoule and incubate at 55–60 °C (ideally with an unprocessed control).
• Read the color at 24 h: purple = negative (correct); yellow = positive (failure). Record the result and dispose of positives according to regulations. 
   

ADVANTAGES

• Easy to use and visible result within 24 h.
• Hermetic sealing (minimizes contamination risks).
• Cost savings in routine quality control.
• Lot number and expiry date identified on each vial. 
   

PRECAUTIONS

• Steam only: do not use for EO, dry heat, chemical vapors, radiation, or other processes.
• Single use: do not reuse.
• Do not reuse the sterilizer until a negative result is obtained. Use PPE (gloves/goggles) when handling. 
   

WASTE DISPOSAL

• Record positives and discard immediately.
• Comply with local regulations; as reference, re-sterilize positives: 121 °C/≥ 20 min, 132 °C/≥ 15 min (gravity) or 134 °C/≥ 10 min (vacuum). 
   

STORAGE
Protect from direct sunlight; store dry, 10–30 °C, RH 30–80%. Do not freeze or store near sterilizing/chemical agents.