Autoclaving is used to sterilise culture media and surgical instruments. Which biological indicator is used to monitor the efficacy of steam autoclaving (121°C/15 psi for 15 minutes)?
- A Geobacillus stearothermophilus spore strips ✓
- B Bacillus subtilis var. globigii (B. atrophaeus) spore strips
- C Clostridium sporogenes spore suspension
- D Candida albicans ATCC 10231 suspension
Correct answer: A. Geobacillus stearothermophilus spore strips
Explanation
Geobacillus stearothermophilus (formerly Bacillus stearothermophilus) spores are the internationally recognised biological indicator for steam sterilisation monitoring because they are the most heat-resistant non-pathogenic spores, with a D-value at 121°C that requires standard autoclaving conditions for complete kill. B. atrophaeus (B. subtilis var. globigii) is the biological indicator for dry heat sterilisation and ethylene oxide sterilisation. C. sporogenes is used as a BI for steam in some older methods. C. albicans is used for monitoring disinfectants.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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