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The only direct measure of sterilizer lethality: With BIs, dead bugs don't lie

A biological indicator (BI) is the only type of monitor that provides direct evidence that sterilization process conditions are sufficient to kill spores. It uses microbes that are highly resistant to the type of sterilization process you are monitoring.

When the high number of highly resistant bugs contained inside the BI die during sterilization, you can be confident that the fewer, less resistant microorganisms found on medical devices should have also been killed. The lethality of your sterilizer is assured.

BIs can detect even marginal sterilization failures that result from inability to reach temperature, inadequate air removal or superheated steam.

BIs are considered the "gold standard" of load sterilization monitoring. They are widely recommended as the preferred device for monitoring and releasing loads.

How a Self-Contained BI Works

A self-contained BI consists of a known population of bacterial spores that are highly resistant to the mode of sterilization that you are monitoring. For example:

  • Geobacillus stearothermophilus is the highly resistant spore used to monitor steam, hydrogen peroxide gas plasma and ozone sterilization.

Figure 1: Components of a Self-Contained 3M™ Attest™ 1292 Rapid Readout Biological Indicator

The self-contained 3M™ Attest™ Biological Indicators consist of a spore strip (spores that are coated on a paper strip) enclosed in a plastic vial along with growth medium contained in a crushable glass ampoule. The cap is designed to allow sterilant to penetrate into the plastic vial, killing the spores and demonstrating that sterilization conditions were met.

After exposure to the sterilization process, BIs must be incubated to determine if any spores survived. Spores start to grow when they come in contact with the nutrients contained in the growth medium and when incubated at the correct temperature.