Which of the following is an example of disinfection rather than sterilization?

• A. Autoclaving eliminates all microorganisms and spores.
• B. Bleach wipe on a nonporous surface is disinfection.
• C. Ethanol on skin sterilizes the skin.
• D. Filtration of air sterilizes rooms.

Answer: (B)

Disinfection reduces pathogenic microbes on inanimate surfaces without achieving a truly sterile state. Sterilization, on the other hand, means destroying or removing all viable microorganisms, including spores. Autoclaving uses heat and moisture to kill everything, so it sterilizes. A bleach wipe on a nonporous surface lowers the microbial load and is used to disinfect, not to sterilize. Ethanol on skin is an antiseptic, which decreases surface microbes but doesn’t sterilize the skin. Filtration of air reduces the number of microbes in the environment but doesn’t guarantee complete removal of all viable organisms, so it’s not considered sterilization.