What type of indicator is used to test the effectiveness of sterilization processes?

The type of indicator used to test the effectiveness of sterilization processes is a biological indicator. Biological indicators contain live spores of a specific microorganism that are highly resistant to the sterilization method being evaluated. For instance, the spores of Bacillus stearothermophilus are commonly used for steam sterilization, and those of Bacillus subtilis for dry heat or ethylene oxide sterilization.

When a biological indicator is exposed to the sterilization process and then incubated, a lack of growth indicates that the sterilization conditions were effective in destroying the spores, confirming that the process can be trusted to eliminate viable microorganisms. The use of biological indicators is crucial in environments such as hospitals or laboratory settings, where the sterility of instruments and materials can have significant implications for health and safety.

In contrast, electrical, chemical, and visual indicators serve different purposes. Electrical indicators monitor the power or readiness of sterilization equipment, chemical indicators change color or provide a visual cue based on temperature or pressure but do not indicate whether spores were killed, and visual indicators simply provide an observable sign (like a tape that changes color) without confirming microbial destruction. Thus, biological indicators are the most reliable method for ensuring the efficacy of sterilization processes.