This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
Effective mode of sterilization is: September 2005 
Select and explain. 
A. Hot water, B. Steam under pressure, C. Steam at atmospheric pressure, D. Dry heat
B: Steam under pressure
Answer: B: Steam under pressure 
Explanation: Ans. B: Steam under pressure Boiling and steam at atmospheric pressure are ineffective means of killing bacterial spores. Boiling requires prolonged period of boiling for killing spores whereas steam at atmospheric pressure may fail with spores of ceain anaerobes and thermophiles. Nothing sho of autoclaving at high pressure can destroy spores and ensure sterilization.