Question 1

Which of the following best describes the difference between disinfection and sterilization?

Accepted Answer

Sterilization destroys all microorganisms and viruses on an object, while disinfection only destroys most microorganisms and viruses on nonliving tissue.

Question 2

A hospital is preparing surgical instruments for reuse. Which method would be most appropriate to ensure all microbial life, including endospores, is destroyed?

Accepted Answer

Autoclaving at 121ºC, 15 psi for 15 minutes

Question 3

Which of the following organisms is most resistant to antimicrobial agents, according to the susceptibility chart?

Accepted Answer

Prions

Question 4

A food processing plant wants to extend the shelf life of strawberries without using heat. Which physical method would be most effective?

Accepted Answer

Irradiation with gamma rays

Question 5

Which of the following statements about decimal reduction time (D-value) is correct?

Accepted Answer

It is the time required to reduce a microbial population by 90% at a specific temperature.

Question 6

Why is hydrogen peroxide not a good choice for treating open wounds?

Accepted Answer

Catalase in human tissues breaks it down before it can act as a disinfectant.

Question 7

Which of the following best explains why moist heat is generally more effective than dry heat for microbial control?

Accepted Answer

Moist heat denatures proteins and destroys membranes more rapidly due to better heat penetration.

Question 8

A laboratory is using a HEPA filter in a biological safety cabinet. What is the primary purpose of this filter?

Accepted Answer

To remove airborne microbes from the air entering and leaving the cabinet

Question 9

Which of the following chemical agents is most appropriate for sterilizing heat-sensitive medical equipment in a closed chamber?

Accepted Answer

Gaseous agents such as ethylene oxide

Question 10

A researcher is comparing the effectiveness of two disinfectants using the use-dilution test. What result indicates the more effective agent?

Accepted Answer

The agent that prevents microbial growth at the highest dilution

Question 11

Which of the following best describes the action of quaternary ammonium compounds (quats)?

Accepted Answer

They denature proteins and disrupt cell membranes, acting as low-level disinfectants.

Question 12

Which of the following is a limitation of using boiling as a method of microbial control?

Accepted Answer

Boiling does not kill endospores, protozoan cysts, and some viruses.

Question 13

A dairy company uses pasteurization for milk. Which statement is correct regarding this process?

Accepted Answer

Pasteurization reduces microbial numbers but heat-tolerant microbes may survive.

Question 14

Which of the following best explains why high concentrations of salt or sugar are used to preserve foods?

Accepted Answer

They create a hypertonic environment, causing microbial cells to lose water and inhibiting growth.

Question 15

Which biosafety level (BSL) is required for handling microbes that cause severe or fatal diseases, such as Ebola virus?

Accepted Answer

BSL-4

Question 16

A scientist is using lyophilization to preserve a bacterial culture. What is the main advantage of this method?

Accepted Answer

It prevents the formation of damaging ice crystals, allowing long-term preservation.

Question 17

Which of the following is a potential risk associated with the use of gaseous agents for sterilization?

Accepted Answer

They can be hazardous, explosive, poisonous, and potentially carcinogenic.

Question 18

Which of the following best describes the effect of nonionizing radiation, such as UV light, on microbial cells?

Accepted Answer

It causes the formation of pyrimidine dimers in DNA, inhibiting replication.

Question 19

Which of the following is a reason why the use of antiseptic and disinfectant chemicals can promote the development of resistant microbes?

Accepted Answer

Sublethal exposure allows some microbes to survive and adapt, leading to resistance.

Controlling Microbial Growth in the Environment: Principles and Methods

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