Which type of sterilization indicator confirms actual microbial kill in a load?

• A. A biological indicator, which uses resistant spores to validate sterilization efficacy.
• B. A chemical indicator that changes color to indicate exposure.
• C. A physical indicator like a temperature gauge.
• D. A document stating sterilization occurred.

Answer: (A)

Proving actual microbial kill requires evidence from a test that directly demonstrates inactivation of microorganisms. A biological indicator does this by containing highly resistant spores and placing them in the load. After the sterilization cycle, the indicator is incubated; if no growth appears, it shows that even the toughest spores were killed, indicating the entire load achieved sterility. If growth occurs, the cycle didn’t achieve sterility and the load must be reprocessed and investigated.

Chemical indicators merely show that the sterilant contacted the items and that required exposure conditions were met; physical indicators track parameters like temperature or time but don’t confirm that microbes were killed; a document stating sterilization occurred doesn’t verify the actual microbial result. Hence, the biological indicator uniquely confirms actual microbial kill in a load.