Which type of Bacillus is used to test efficacy of sterilisation by an instrument shown below?
A. Bacillus anthracis.
B. Bacillus pumilis.
C. Bacillus stearothermophilus.
D. Coxiella burnetti.
Ans:C. Bacillus stearothermophilus.
The instrument shown in the picture above is an autoclave.
- It is a process designed to kill all microbes.
- Autoclave uses moist heat for sterilization.
- Because we can’t actually test whether all microbes are killed during the sterilization process, the next best thing is to determine whether the process kills the most resistant microbe.
- Bacterial spores have been selected as the most resistant type of microbe, and provide the foundation for the process of sterilization.
- For various methods of sterilization following biological indicators are used :-
|Type of Sterilization||Spore used|
|Moist heat (autoclave)||Bacillus stearothermophilus|
|Dry heat (hot air oven)||Bacillius subtilis|
|Ionizing radiation||Bacillus pumilis|
|Gas sterilization (ethylene oxide)||Bacillus subtilis|
|Plasma sterilization||Bacillus stearothemophilus|
- For moist heat sterilization process, spores of suitable strains Bacillus stearothermophilus are commercially available as biological indicators and frequently employed.
- Other heat-resistant spore-forming microorganisms such as Clostridium sporogenes,Bacillus subtilis and Bacillus coagulans have also been used in the validation of moist heat sterilization processes.