Q: Which of the following is the correct equation for decimal reduction time (DRT)?

$$ DRT = \text{Minutes to kill 90\% of a specific population of bacteria at a given temperature} $$

Question 1

Which of the following best describes the process of sterilization?

Accepted Answer

The removal or destruction of all forms of microbial life, including endospores.

Question 2

A hospital autoclave is used to sterilize surgical instruments. If a 9000-milliliter bottle is being sterilized, why does it require a longer sterilization time compared to a small flask?

Accepted Answer

Larger containers require more time for the contents to reach the sterilization temperature.

Question 3

Which of the following terms refers to the inhibition, but not killing, of microbes?

Accepted Answer

Bacteriostasis

Question 4

A chemical agent that damages the plasma membrane of bacteria is most likely to:

Accepted Answer

Cause leakage of cellular contents.

Question 5

Which of the following is the correct equation for decimal reduction time (DRT)?

Accepted Answer

$$ DRT = 	ext{Minutes to kill 90\% of a specific population of bacteria at a given temperature} $$

Question 6

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

Accepted Answer

Filtration

Question 7

Why are gram-negative bacteria generally more resistant to chemical biocides than gram-positive bacteria?

Accepted Answer

They have an outer membrane that restricts entry of many chemicals.

Question 8

Which of the following statements about alcohols as antimicrobial agents is TRUE?

Accepted Answer

Alcohols denature proteins and dissolve lipids, but require water for maximum effectiveness.

Question 9

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

Accepted Answer

The disinfectant is highly effective against the test organism.

Question 10

Which of the following chemical agents is considered a sporicide and can be used for chemical sterilization?

Accepted Answer

Glutaraldehyde

Question 11

Which of the following best explains why high concentrations of salt or sugar can preserve food?

Accepted Answer

They create a hypertonic environment, causing plasmolysis in microbes.

Question 12

Which of the following is a correct description of pasteurization?

Accepted Answer

A process that reduces spoilage organisms and pathogens in food by heating it to 72°C for 15 seconds.

Question 13

Which of the following statements about ionizing radiation is TRUE?

Accepted Answer

It kills microbes by causing lethal mutations in DNA.

Question 14

A patient is treated with a chemical that inhibits microbial growth but does not kill the microbes. This chemical is best described as:

Accepted Answer

A bacteriostatic agent

Question 15

Which of the following is a major advantage of glutaraldehyde over other chemical disinfectants?

Accepted Answer

It is one of the few liquid chemical sterilizing agents.

Question 16

Which of the following best describes the action of phenolic compounds as disinfectants?

Accepted Answer

They disrupt plasma membranes, causing leakage of cellular contents.

Question 17

A nurse uses an alcohol swab on a patient's skin before an injection. This is an example of:

Accepted Answer

Degerming

Question 18

Which of the following is the primary reason why endospores are difficult to destroy?

Accepted Answer

They have tough, protective protein coats and are metabolically inactive.

Question 19

Which of the following is a correct application of the use-dilution test?

Accepted Answer

To evaluate the effectiveness of a disinfectant against specific bacteria on metal or glass cylinders.

Question 20

A food processing plant wants to sterilize heat-sensitive medical implants. Which method is most appropriate?

Accepted Answer

Supercritical fluid sterilization

Chapter 7: The Control of Microbial Growth – Study Notes

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