How often should biological indicators be used to monitor steam sterilizers, and what is their purpose?

• A. Weekly; they verify that sterilization conditions achieved microbial kill (spore death) in the load.
• B. Daily; they measure temperature of the room.
• C. Monthly; they record operator performance.
• D. Yearly; they check for chemical residue.

Answer: (A)

Biological indicators are used to confirm that the steam sterilization cycle actually achieves microbial kill, not just that the load reached a certain temperature. They contain highly resistant bacterial spores and are placed in or with a typical load. After the cycle, the indicators are incubated; if no growth occurs, it shows the sterilizer successfully killed the spores in that run. If growth appears, the cycle did not achieve the necessary lethality and the device requires maintenance or revalidation before the loads can be considered sterile.

Weekly testing is a common, practical frequency that provides ongoing assurance without being excessively burdensome. It directly supports confirming the sterilizer’s ability to achieve spore death in real-world loads. The other options miss the point: measuring room temperature isn’t about microbial kill, monthly checks of operator performance aren’t about sterilization efficacy, and yearly checks for chemical residue aren’t what biological indicators assess.