Which biological indicator is used to verify steam sterilization effectiveness?

The biological indicator used to verify steam sterilization effectiveness is Geobacillus stearothermophilus. This microorganism is a thermophilic spore-forming bacterium that is highly resistant to heat and is utilized specifically in monitoring the efficacy of steam sterilization processes.

When steam sterilization is performed, the presence of viable spores of Geobacillus stearothermophilus in the sterilization process acts as a reliable indicator; if the spores are killed, it indicates that the conditions (temperature and time) during sterilization were sufficient to achieve sterility. As such, this organism is routinely utilized in quality assurance programs within healthcare settings to ensure that autoclaves and other steam sterilization methods are functioning correctly.

Other options, while also spore-forming bacteria, do not serve the same purpose in the context of verifying steam sterilization processes. Their resistance profiles and environmental preferences differ, meaning they are not ideal indicators for this specific type of sterilization.