Question 1

Which of the following best describes the goal of pathogen eradication?

Accepted Answer

To eliminate all pathogens in any reservoir so that new cases cannot occur.

Question 2

A microbiology lab needs to ensure that all microorganisms, including endospores, are destroyed in a liquid broth before use. Which method should be used?

Accepted Answer

Sterilization using an autoclave

Question 3

Which of the following statements about herd immunity is correct?

Accepted Answer

The required level of immunity varies based on the infectiousness of the disease.

Question 4

If a disease has a basic reproduction number $$R_0 = 18$, what is the minimum percentage of the population that must be immune to achieve herd immunity? (Use the formula H = 1$$ - \frac{1}{$$R_0$$}$$)

Accepted Answer

$$H = 1 - \frac{1}{18} = 0.94 or 94$$%

Question 5

Which of the following is an example of a physical method to control microbial growth?

Accepted Answer

Applying UV radiation to sterilize laboratory benches

Question 6

Why is moist heat more effective than dry heat for sterilization?

Accepted Answer

Moist heat denatures proteins more efficiently and penetrates cells better.

Question 7

A hospital uses UV lamps to sterilize air and surfaces in operating rooms. What is the main limitation of this method?

Accepted Answer

UV radiation cannot penetrate deeply into solid materials.

Question 8

Which of the following best describes the decimal reduction time ($$D$$ value) in microbial control?

Accepted Answer

The time required to reduce the microbial population by 90%.

Question 9

A solution containing proteins must be sterilized, but cannot be heated. Which method is most appropriate?

Accepted Answer

Filtration through a 0.2 μm membrane

Question 10

Which of the following chemical agents acts primarily by denaturing proteins?

Accepted Answer

Phenol

Question 11

Which food preservation method works by removing water to stop microbial metabolic activities?

Accepted Answer

Desiccation

Question 12

A food product label lists sodium nitrite and potassium sorbate as ingredients. What is their primary function?

Accepted Answer

They act as preservatives to inhibit microbial growth.

Question 13

Which of the following is a key difference between sterilization and pasteurization?

Accepted Answer

Sterilization kills all microorganisms, while pasteurization reduces the number of pathogens without killing all microbes.

Question 14

Which of the following strategies is NOT typically used by public health departments to eliminate a human-specific infection?

Accepted Answer

Allowing natural infection to spread unchecked

Question 15

Which of the following statements about the use of cold temperatures in food preservation is correct?

Accepted Answer

Freezing and refrigeration slow or stop the growth of most pathogens by decreasing metabolic activity.

Question 16

Which of the following is a real-world example of degerming?

Accepted Answer

Washing hands with soap and water before surgery

Question 17

Which of the following best explains why smallpox was successfully eradicated?

Accepted Answer

Smallpox only infects humans and has no animal reservoir.

Question 18

Which of the following is a limitation of using filtration to sterilize a solution?

Accepted Answer

Viruses can pass through standard 0.2 μm filters.

Question 19

Which of the following is the best example of sanitization?

Accepted Answer

Washing dishes in hot, soapy water in a restaurant

Question 20

A batch of milk is treated at $$72^\circ C$$ for 15 seconds. What process is being used?

Accepted Answer

Flash pasteurization

unit 5 lecture 2

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