Certification Board for Sterile Processing and Distribution (CBSPD) Sterile Processing Technician Practice Exam

The correct choice is Bacillus atrophaeus. This microorganism is specifically selected for biological monitoring of dry heat sterilizers because it is a spore-forming bacterium that can withstand high temperatures, making it an ideal indicator of the efficacy of the sterilization process. When using Bacillus atrophaeus, the spores are subjected to the sterilization cycle, and post-sterilization, microbiological testing determines whether any spores survived. The presence of viable spores indicates a failure in the sterilization process, while the absence confirms that the process was effective.

In contrast, Geobacillus stearothermophilus is the standard for monitoring steam and chemical sterilization processes, as it thrives in moist environments. Bacillus subtilis is often used for other testing purposes but not specifically for dry heat, as it does not demonstrate the same level of heat resistance as Bacillus atrophaeus. Mycobacterium tuberculosis is not suitable for sterilization monitoring; it is a pathogenic organism and not a spore-forming bacterium, making it inappropriate for this role. Thus, Bacillus atrophaeus is the correct microorganism to use for biological monitoring of dry heat sterilizers due to its heat resistance and spore-forming capabilities.