Which statement about autoclave sterilization validation using Bacillus stearothermophilus (Geobacillus stearothermophilus) spores is correct?

• A Bacillus subtilis spores are the biological indicator for autoclaving
• B Spores of B. stearothermophilus are used because they are the most heat-resistant bacterial spores known and survive 134°C/3 min; failure to kill them confirms sterilization failure ✓
• C B. stearothermophilus is used for dry heat oven validation
• D The biological indicator for EO gas sterilization is B. stearothermophilus

Explanation

Geobacillus stearothermophilus (formerly B. stearothermophilus) spores are the standard biological indicator for moist heat (autoclave) sterilization because they are among the most resistant endospores to saturated steam — D-value at 121°C is 1.5–4 minutes. The autoclave cycle (121°C/15 min or 134°C/3 min) must kill these spores; a positive culture after cycling indicates sterilization failure. Bacillus subtilis (Bacillus atrophaeus) spores are used for ethylene oxide (EO) gas sterilization and dry heat validation. B. pumilus is used for gamma irradiation validation.

Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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