What is the purpose of a biological indicator in sterilization?

• A. To demonstrate that the sterilizer achieved a sterilizing condition by killing a highly resistant organism.
• B. To measure how clean the water used.
• C. To determine the pH of the disinfectant.
• D. To label the pack with the date.

Answer: (A)

Biological indicators test whether the sterilization cycle actually achieves a sterilizing condition by proving that the most resistant organisms present in the load are killed. They use spores of highly resistant bacteria, placed in the hardest spot to sterilize, and after the cycle are incubated to see if any growth occurs. If there’s no growth, it indicates the sterilizer reached the required temperature and time and properly penetrated the load. If growth is detected, the cycle did not achieve sterilization and corrective action is needed. The other options don’t verify sterility: they involve measuring water cleanliness, pH of the disinfectant, or labeling the pack, none of which confirm that all microorganisms were killed.