Question 1

Which of the following best describes the term 'microbial death rate' as used in microbial control?

Accepted Answer

The rate at which a constant percentage of the microbial population is killed per unit time under specific conditions.

Question 2

A hospital is deciding between two disinfectants. Disinfectant A has a phenol coefficient of 0.8, and Disinfectant B has a phenol coefficient of 2.0. Which statement is correct?

Accepted Answer

Disinfectant B is more effective than phenol.

Question 3

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

Accepted Answer

Prions

Question 4

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

Accepted Answer

Moist heat denatures proteins and destroys membranes more efficiently due to better heat transfer.

Question 5

A laboratory is using an autoclave set at 121°C and 15 psi for 15 minutes. What is the primary purpose of this process?

Accepted Answer

To sterilize equipment by killing all forms of microbial life, including endospores

Question 6

Which of the following best explains why Bacillus endospores are used as sterility indicators in autoclaving?

Accepted Answer

They are highly resistant, so their destruction indicates effective sterilization.

Question 7

A food processing plant wants to preserve fruit using a physical method that inhibits microbial growth by removing water. Which method should they use?

Accepted Answer

Desiccation

Question 8

Which of the following statements about the 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 9

A patient with a wound is treated with hydrogen peroxide. Why might this not be effective for sterilizing the wound?

Accepted Answer

Hydrogen peroxide is inactivated by catalase present in tissues.

Question 10

Which of the following is a correct application of the use of HEPA filters in a laboratory?

Accepted Answer

Filtering air to remove microbes in biological safety cabinets

Question 11

A researcher is working with a virus that causes severe and often fatal disease in humans. Which biosafety level (BSL) is required for this work?

Accepted Answer

BSL-4

Question 12

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

Accepted Answer

They disrupt cellular membranes, leading to cell death.

Question 13

Why does milk eventually spoil even after pasteurization?

Accepted Answer

Pasteurization only kills pathogenic and most non-pathogenic microbes, but heat-tolerant and heat-loving microbes survive.

Question 14

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 15

A solution is treated with an agent that causes the formation of pyrimidine dimers in DNA. Which type of physical control is being used?

Accepted Answer

Nonionizing radiation (UV light)

Question 16

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 17

A laboratory technician needs to sterilize a solution that is heat-sensitive. Which method should be used?

Accepted Answer

Filtration through a membrane filter

Question 18

Which of the following statements about aldehydes as antimicrobial agents is correct?

Accepted Answer

They act by cross-linking functional groups in proteins and nucleic acids, leading to denaturation.

Question 19

A patient is given a vaccine preserved with thimerosal. What is the primary antimicrobial mechanism of thimerosal?

Accepted Answer

It denatures proteins by binding to sulfur groups.

Question 20

Which of the following is a limitation of using alcohols as disinfectants?

Accepted Answer

They are not effective against bacterial endospores or fungal spores.

Controlling Microbial Growth in the Environment: Principles and Methods

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