Biological indicators
Biological sterilization indicators are devices that allow you to evaluate the effectiveness of the sterilization process, i.e. the killing of microorganisms in the vegetative or spore phase.
The biological indicators are made up of standardized bacterial spores inoculated on different types of support which, in addition to allowing their appropriate use, emulate the process that leads to the reduction of the microbial load.
Types of sterilization
The bacterial spores used in biological indicators are selected by type, population and resistance to specific sterilizing agents, such as:
- steam
- ethylene oxide
- hydrogen peroxide
- dry heat
- radiation
- chlorine dioxide
- formaldehyde
Spore carriers
Chosen based on the type of sterilization and are:
- paper strips, threads and discs (in sachets or bare)
- steel discs and bars (in sachet or bare)
- paper or steel discs (self-contained systems in plastic tubes)
- suspensions in culture medium (glass ampoules)
- suspensions in aqueous solution
Spores used
- Geobacillus stearothermophilus 7953
- Geobacillus stearothermophilus 12980
- Bacillus atrophaues 9372
- Bacillus atrophaeus NRRL B-4418
- Bacillus pumilus 27142
- Bacillus subtilis 35021
They are regulated by ISO 11138 Sterilization of health care products - Biological indicators and by pharmacopoeias.