Question 1

Which of the following statements best explains why prions are more resistant to antimicrobial agents than bacterial endospores?

Accepted Answer

Prions are composed of abnormal proteins that are highly stable and resistant to denaturation.

Question 2

A hospital needs to sterilize heat-sensitive liquid media. Which method would be most appropriate?

Accepted Answer

Filtration using a 0.22 μm membrane filter

Question 3

Which biosafety level (BSL) is required for handling pathogens like Ebola virus, and why are the suits used at this level pressurized?

Accepted Answer

BSL-4; to ensure that if the suit is punctured, air flows out rather than in, preventing pathogen entry

Question 4

Which of the following is the correct definition of thermal death point?

Accepted Answer

The lowest temperature that kills all cells in a broth in 10 minutes

Question 5

A laboratory is using a high-efficiency particulate air (HEPA) filter in a biological safety cabinet. What is the primary function of the HEPA filter?

Accepted Answer

To remove airborne microbes and particles from the air entering and exiting the cabinet

Question 6

Which of the following moist heat treatments is most likely to sterilize milk, allowing it to be stored at room temperature?

Accepted Answer

Ultra-high-temperature sterilization at 140°C for 1–3 seconds

Question 7

Why is slow freezing generally more effective at controlling microbial growth than quick freezing?

Accepted Answer

Slow freezing causes more ice crystals to form, which can puncture cell membranes.

Question 8

Which of the following best describes the decimal reduction time (D-value) shown in the microbial death rate graph?

Accepted Answer

The time required to reduce the microbial population by 90% at a specific temperature

Question 9

Which of the following organisms would be most susceptible to a low-level germicide?

Accepted Answer

Enveloped viruses

Question 10

A researcher needs to preserve a bacterial culture for several years without damaging the cells. Which method should be used?

Accepted Answer

Lyophilization

Question 11

Which of the following statements about osmotic pressure is correct?

Accepted Answer

Fungi are generally more resistant to hypertonic environments than bacteria.

Question 12

Which of the following is NOT a factor that affects the efficacy of antimicrobial methods?

Accepted Answer

The color of the microbial colony

Question 13

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

Accepted Answer

Moist heat denatures proteins and destroys membranes more efficiently at lower temperatures.

Question 14

Which of the following best describes the function of an autoclave?

Accepted Answer

It applies pressure to boiling water, increasing the boiling temperature and sterilizing materials.

Question 15

A laboratory is working with a pathogen that can cause severe or fatal disease in humans. Which biosafety level should be used?

Accepted Answer

BSL-4

Question 16

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

Accepted Answer

Boiling is ineffective against bacterial endospores and some viruses.

Question 17

Which pore size membrane filter would be most appropriate to remove all bacteria from a liquid sample?

Accepted Answer

$$0.22\ \mu m$$

Question 18

Which of the following best explains why organic materials can interfere with the efficacy of chemical disinfectants?

Accepted Answer

Organic materials can inactivate chemical disinfectants and block their penetration.

Question 19

Which of the following is the ultimate means of sterilization for contaminated materials?

Accepted Answer

Incineration

Question 20

A dairy company wants to ensure that its milk is free from all pathogens and can be stored at room temperature. Which process should it use?

Accepted Answer

Ultra-high-temperature sterilization at 140°C for 1–3 seconds

Controlling Microbial Growth in the Environment: Methods and Principles

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