Question 1

Which of the following best describes the process of sterilization?

Accepted Answer

The removal or destruction of all microbial life, including endospores

Question 2

A hospital autoclave is set to operate at $$121\ ^\circ C$$ and 15 psi for 15 minutes. What is the primary reason large containers require longer sterilization times?

Accepted Answer

It takes longer for the center of large containers to reach the required temperature

Question 3

Which of the following statements about the decimal reduction time (DRT) is correct?

Accepted Answer

It is the time required to kill 90% of a specific population of bacteria at a given temperature

Question 4

A solution contains $$1 	imes 10^6$ bacteria. If a microbial control agent kills 90% of the bacteria every minute, how many bacteria remain after 3 minutes?

Accepted Answer

$$1 	imes 10^3$

Question 5

Which of the following is a reason why gram-negative bacteria are generally more resistant to chemical biocides than gram-positive bacteria?

Accepted Answer

Their outer membrane contains lipopolysaccharides that restrict entry of biocides

Question 6

Which physical method of microbial control is most appropriate for sterilizing heat-sensitive solutions such as vaccines?

Accepted Answer

Filtration

Question 7

Why are alcohol-based hand sanitizers ineffective against Clostridium difficile and norovirus?

Accepted Answer

Alcohols are only effective against enveloped viruses and vegetative bacteria

Question 8

Which of the following best explains why a solution with a higher initial microbial load takes longer to sterilize than one with a lower load, assuming the same rate of killing?

Accepted Answer

The rate of killing is proportional to the number of microbes present, so more cycles are needed to reach zero survivors

Question 9

Which of the following chemical agents is most effective for sterilizing medical equipment that cannot withstand heat?

Accepted Answer

Glutaraldehyde

Question 10

A disk-diffusion test is performed with four disinfectants on Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. Which disinfectant is likely to show the largest zone of inhibition for all three organisms?

Accepted Answer

Chlorine

Question 11

Which of the following statements about moist heat sterilization is correct?

Accepted Answer

It denatures proteins and is effective at $$121\ ^\circ C$$ for 15 minutes under pressure

Question 12

Which of the following is a limitation of using ultraviolet (UV) radiation for sterilization?

Accepted Answer

It does not penetrate surfaces and is only effective for surface sterilization

Question 13

Which of the following best describes the action of halogens such as iodine and chlorine in microbial control?

Accepted Answer

They impair protein synthesis and act as oxidizing agents

Question 14

A food processing plant wants to prevent the growth of Clostridium botulinum in canned meats. Which chemical preservative should be used?

Accepted Answer

Nitrites

Question 15

Which of the following is a correct statement about the use-dilution test for evaluating disinfectants?

Accepted Answer

It involves dipping metal cylinders in test bacteria, exposing them to disinfectant, and then culturing to check for survivors

Question 16

Which of the following is the most likely reason why hydrogen peroxide is not a good antiseptic for open wounds?

Accepted Answer

Human tissues contain catalase, which breaks down hydrogen peroxide

Question 17

Which of the following best explains why prions are difficult to destroy using standard sterilization methods?

Accepted Answer

They are resistant to heat, radiation, and most chemicals

Question 18

Which of the following is a real-world application of high-pressure microbial control?

Accepted Answer

Preserving fruit juices by denaturing proteins and altering carbohydrate structure

Question 19

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

Accepted Answer

Glutaraldehyde is fair against endospores and good against mycobacteria

Question 20

A patient is treated with a disinfectant that damages plasma membranes. Which of the following is a potential risk if the disinfectant is used on human skin?

Accepted Answer

It may cause leakage of cellular contents from human cells

Chapter 7: The Control of Microbial Growth – Study Notes

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