Question

Which of the following bacteria used as an index organisms for Milk sterilization?

• A. Bacillus stearothermophilus
• B. Bacillus subtilis
• C. Bacillus megaterium
• D. Bacillus cereus

Hint:

Remember:
- Pasteurization index = Coxiella burnetii
- Sterilization index = Bacillus stearothermophilus

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Sterilization aims to destroy all viable microorganisms and their highly resistant spores.
To validate a sterilization process, we use a highly heat-resistant reference organism as an index.

Step 2: Detailed Explanation:
- {Geobacillus stearothermophilus (formerly known as {Bacillus stearothermophilus) is a thermophilic, spore-forming bacterium.
- Its endospores are exceptionally resistant to wet heat, requiring temperatures above \(121^\circ\text{C}\) to be destroyed.
- Because of this extreme thermal resistance, it is used as the standard biological indicator (index organism) to evaluate and validate the efficiency of steam sterilization, autoclaving, and ultra-high-temperature (UHT) processing in the dairy and food industries.
- If the thermal process successfully inactivates B. stearothermophilus spores, it is assumed that all other pathogens and vegetative cells have also been destroyed.

Step 3: Final Answer
Bacillus stearothermophilus is used as the index organism for milk sterilization.