Exercise 1: Moist and dry heat

1. How are microorganisms destroyed by moist heat? By dry heat?

2. Are some microorganisms more resistant to heat than others? Why?

3. Is moist heat more effective than dry heat? Why?

4. Why does dry heat require higher temperatures for longer time periods to sterilize than does moist heat?

5. What is the relationship of time to temperature in heat sterilization? Explain.

Exercise 2: The autoclave

1. Define the principles of sterilization with an autoclave and with a dry heat oven.

2. What pressure, temperature, and time are used in routine autoclaving?

3. What factors determine the time period necessary for steam-pressure sterilization? Dry-heat oven sterilization?

4. Why is it necessary to use bacteriologic controls to monitor heat- sterilization techniques?

5. When running an endospore control of autoclaving technique, why is one endospore preparation incubated without heating?