A laboratory wants to sterilize empty glass petri dishes, oil-based ointments and powdered substances before use. Which sterilization method and standard cycle is appropriate?
- A Hot air oven at 160°C for 2 hours ✓
- B Autoclave at 121°C for 15 minutes
- C Ethylene oxide at 55°C for 4 hours
- D Tyndallization at 100°C on three successive days
Correct answer: A. Hot air oven at 160°C for 2 hours
Explanation
Dry heat in the hot air oven at 160°C held for 2 hours is the standard cycle for glassware, oils, powders and sharp instruments that would be damaged by moisture. Dry heat kills by oxidative destruction of cell constituents rather than protein coagulation. Autoclaving cannot be used because steam does not penetrate oils and powders, and moisture would ruin dry glassware. Tyndallization is reserved for heat-labile fluids.
Reference: Ananthanarayan and Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.