Certified Surgical Technologist (CST) Practice Exam

The most reliable method for determining the efficiency of moist heat sterilizers is the controlled use of biological indicators containing which organism?

1. Bacillus stearothermophilus

2. Clostridium tetani

3. Bordetella pertussis

4. Corynebacterium diptheria

The correct answer is: Bacillus stearothermophilus

The effectiveness of moist heat sterilizers is best assessed through the use of biological indicators, and Bacillus stearothermophilus is the organism of choice for this purpose. This specific bacterium is a heat-resistant spore-forming organism, which makes it an ideal challenge organism for validating the sterilization process. When subjected to the moist heat sterilization process, such as autoclaving, the spores of Bacillus stearothermophilus are exposed to steam and high temperatures. If the sterilization process is successful, the spores will be inactivated. The monitoring system requires that specific conditions, including time and temperature, are met to ensure the effectiveness of the sterilization process. Using Bacillus stearothermophilus is effective because its spores are more resistant to heat compared to many other microorganisms. If they are proven to have been killed, it gives a strong indication that other, less resistant microorganisms have also been inactivated. In contrast, the other organisms listed—Clostridium tetani, Bordetella pertussis, and Corynebacterium diphtheriae—are not used for this specific purpose. They either do not provide the same level of reliability as biological indicators in moist heat sterilization or do not produce