Which of the following is a limitation of the autoclave in microbiological sterilization?

• A. It is ineffective against bacterial spores.
• B. It requires the use of toxic chemicals.
• C. It operates at temperatures below 50 ^ext{o} ext{C}.
• D. It cannot sterilize heat-sensitive materials.

Answer: (D)

Verified step by step guidance

1. Understand the purpose of an autoclave: it is a device used for sterilization by applying high-pressure saturated steam at high temperatures, typically around 121\textdegree C, to kill all forms of microbial life including bacterial spores.
2. Review the options given and recall that autoclaves are effective against bacterial spores due to the high temperature and pressure, so the statement 'It is ineffective against bacterial spores' is incorrect.
3. Recognize that autoclaves do not require toxic chemicals; sterilization is achieved through steam and pressure, so 'It requires the use of toxic chemicals' is not a limitation.
4. Note that autoclaves operate at temperatures well above 50\textdegree C, usually around 121\textdegree C, so 'It operates at temperatures below 50\textdegree C' is false.
5. Identify that the main limitation of autoclaves is their inability to sterilize heat-sensitive materials because the high temperature and pressure can damage such items, making 'It cannot sterilize heat-sensitive materials' the correct limitation.