AP-Micro Microbiology: Sterilization, Disinfection, and Infection Control

Question 1

Which sterilization method uses saturated steam under pressure to destroy all microorganisms, including bacterial endospores?

Accepted Answer

Autoclave (moist heat)

Answer

Autoclaving uses saturated steam at 121°C and 15 psi for 15–20 minutes, which is sufficient to denature proteins and kill all microbial life including heat-resistant spores.

Question 2

What are the standard conditions for gravity-displacement autoclave sterilization?

Accepted Answer

121°C for 15–20 minutes at 15 psi

Answer

Standard gravity autoclaving requires 121°C, 15 psi, for a minimum of 15–20 minutes to ensure complete sterilization of wrapped instruments.

Question 3

Which sterilization method is most appropriate for heat-labile materials such as plastics, rubber tubing, and electronic components?

Accepted Answer

Ethylene oxide (EtO) gas

Answer

Ethylene oxide is a low-temperature (37–63°C) alkylating gas that sterilizes heat-sensitive materials without causing thermal damage.

Question 4

Dry heat sterilization of glassware and metal instruments typically requires which conditions?

Accepted Answer

160°C for 1–2 hours

Answer

Dry heat sterilization requires 160°C for 1–2 hours (or 170°C for 1 hour) because dry heat is less efficient than moist heat at penetrating and killing microorganisms.

Question 5

Which biological indicator is used to validate the effectiveness of steam autoclave sterilization cycles?

Accepted Answer

Geobacillus stearothermophilus spores

Answer

Geobacillus stearothermophilus (formerly Bacillus stearothermophilus) produces highly heat-resistant spores that serve as the gold-standard biological indicator for autoclave validation.

AP Practice Test

AP Practice Test

AP-Micro Microbiology: Sterilization, Disinfection, and Infection Control