Question 1

Which of the following best describes the decimal reduction time (DRT) in microbial control?

Accepted Answer

The time required to kill 90% of a microbial population at a given temperature.

Question 2

A hospital is sterilizing surgical instruments using an autoclave. Which of the following conditions is most appropriate for effective sterilization?

Accepted Answer

$$121\ ^\circ\mathrm{C} at 15 $$psi for 15 minutes

Question 3

Which of the following statements about the microbial death curve is correct?

Accepted Answer

A logarithmic plot of the number of surviving cells results in a straight line.

Question 4

Which physical method is most suitable for sterilizing heat-sensitive solutions such as certain antibiotics or vaccines?

Accepted Answer

Filtration using membrane filters

Question 5

A food processing plant wants to reduce spoilage organisms and pathogens in milk without sterilizing it. Which process should they use?

Accepted Answer

Pasteurization at $$72\ ^\circ\mathrm{C}$$ for 15 seconds

Question 6

Which of the following is a limitation of alcohol-based hand sanitizers?

Accepted Answer

They are not effective against endospore-forming bacteria such as Clostridium difficile.

Question 7

Which chemical agent is considered a gaseous chemosterilant and is used for sterilizing heat-sensitive medical equipment?

Accepted Answer

Ethylene oxide

Question 8

A laboratory is testing the effectiveness of a new disinfectant using the disk-diffusion method. What does a large zone of inhibition around a disk indicate?

Accepted Answer

The disinfectant is more effective against the test organism.

Question 9

Which of the following best explains why gram-negative bacteria are generally more resistant to biocides than gram-positive bacteria?

Accepted Answer

They possess an outer membrane containing lipopolysaccharides.

Question 10

Which of the following statements about the use of halogens is correct?

Accepted Answer

Iodine is used as an antiseptic, while chlorine is used as a disinfectant.

Question 11

Which of the following is the primary mode of action for phenolic compounds such as those found in Lysol®?

Accepted Answer

Disruption of plasma membranes

Question 12

A patient is treated with a wound dressing containing silver. What is the antimicrobial mechanism of silver?

Accepted Answer

Denaturation of proteins via oligodynamic action

Question 13

Which of the following is a correct statement about the effectiveness of chemical antimicrobials against endospores and mycobacteria?

Accepted Answer

Glutaraldehyde is fair against endospores and good against mycobacteria.

Question 14

Which of the following physical methods of microbial control is most effective for sterilizing disposable medical supplies such as syringes and catheters?

Accepted Answer

Ionizing radiation (gamma rays)

Question 15

A food manufacturer wants to prevent the germination of Clostridium botulinum endospores in canned meats. Which preservative should be used?

Accepted Answer

Nitrites and nitrates

Question 16

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

Accepted Answer

They denature proteins and disrupt plasma membranes.

Question 17

Which of the following factors does NOT increase the effectiveness of a disinfectant?

Accepted Answer

Increasing the concentration of organic matter

Question 18

A laboratory is using a use-dilution test to evaluate a new disinfectant. What is the main purpose of this test?

Accepted Answer

To evaluate the effectiveness of disinfectants against specific microbes

Question 19

Which of the following is a reason why prions are particularly difficult to destroy in a clinical setting?

Accepted Answer

They require immersion in NaOH and autoclaving at $$121\ ^\circ\mathrm{C}$$ for 1 hour.

Question 20

Which of the following statements about peroxygens is correct?

Accepted Answer

Peracetic acid is an effective liquid sterilant for medical equipment.

The Control of Microbial Growth: Principles and Methods

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