1. Flying on an airplane includes lots of individuals in close quarters for potentially long periods of time.

a. What technology do you think airplanes use to reduce the amount of microbes from the air?

b. Despite this control method, there have been a number of documented cases of individuals infected with tuberculosis infecting other passengers during a flight. Explain how you think this happened. Which patients are at highest risk for infection, and what does this tell you about the effectiveness of microbial control on an airplane?

2. The thermal death time for a suspension of Bacillus subtilis endospores is 20 minutes in dry heat and less than 10 minutes in an autoclave. Which type of heat is more effective? Why?

3. A large hospital washes burn patients in a stainless steel tub. After each patient, the tub is cleaned with a quat. It was noticed that 14 of 20 burn patients acquired Pseudomonas infections after being bathed. Provide an explanation for this high rate of infection.

4. If you're on a municipal water supply, the water coming out of your faucet is chlorinated at the water treatment plant.

a. Is the water coming out of your faucet sterile?

b. Does the water still contain chlorine?

c. What are advantages and disadvantages of chlorine compared with other approaches (e.g., UV treatment, treatment with ozone).

5. A low technology approach to treating water in rural locations is to fill clear plastic soda bottles with water and leave it out all day in the sun (e.g., up on a roof).

a. What two factors are most likely at work in controlling microbes in these conditions?

b. What impact does each factor have on the microbes?