A laboratory must sterilise a batch of clean glass petri dishes and a bottle of liquid paraffin. Which hot air oven cycle is the standard recommended schedule for this load?
- A 121 degrees Celsius held for 15 minutes under pressure
- B 160 degrees Celsius held for 2 hours ✓
- C 100 degrees Celsius held for 30 minutes
- D 134 degrees Celsius held for 3 minutes under pressure
Correct answer: B. 160 degrees Celsius held for 2 hours
Explanation
The classic validated hot air oven cycle is 160 degrees Celsius maintained for 2 hours, which kills even bacterial endospores including Geobacillus stearothermophilus. It is suitable for glassware, oils, powders and sharp instruments that cannot be penetrated by steam. The 121 degree and 134 degree cycles are moist heat autoclave schedules requiring saturated steam under pressure, which cannot be achieved inside a dry oven, and boiling achieves disinfection rather than sterilisation.
Reference: Ananthanarayan and Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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