Sterilization practice – concept check: Which of the following methods will NOT achieve true sterilization under the conditions stated (i.e., it may fail to destroy all bacterial endospores)?

Introduction:
Sterilization means the complete destruction of all forms of microbial life, including resistant bacterial endospores. This item asks you to identify the method that does not meet the definition when used exactly as stated.

Given Data / Assumptions:

• Steam at 121°C for 15–20 minutes (autoclaving) is a benchmark sterilization cycle.
• Dry heat at 171°C for 1–2 hours is a recognized sterilization schedule for heat-stable items.
• Glutaraldehyde 2% for 10 hours is a high-level chemical sterilant for devices that cannot be heated.
• Boiling at 100°C for 30 minutes does not reliably kill endospores.

Concept / Approach:
Endospores of Bacillus and Clostridium resist moist heat at 100°C. Boiling achieves disinfection, not assured sterilization. Pressurized steam reaches higher temperatures (121°C) and coagulates spore proteins more effectively; dry heat at specified high temperatures oxidizes cell components; prolonged glutaraldehyde exposure chemically inactivates spores.

Step-by-Step Solution:
List each method and whether it is validated for spores. Recognize that boiling at 100°C is insufficient for spores. Select the single method that fails sterilization: boiling.

Verification / Alternative check:
Biological indicators (e.g., Geobacillus/Bacillus spores) survive boiling but are inactivated by autoclave/dry-heat cycles and approved chemical sterilant exposure.

Why Other Options Are Wrong:
Glutaraldehyde 10 h – high-level sterilant for heat-sensitive devices.
Dry heat 171°C 1–2 h – validated sterilization schedule.
Steam 121°C 15–20 min – standard sterilization cycle.
Pasteurization – also not sterilization, but not one of the original listed four in the stem; included here as a distractor only.

Common Pitfalls:
Equating “boiling” with sterilization; it is only disinfection unless combined with intermittent steaming (tyndallization) or higher pressure/temperature.

Final Answer:
Boiling water at 100°C for 30 minutes.