Question 1

Which of the following best describes the process of sterilization?

Accepted Answer

The removal and destruction of all microbial life, including endospores.

Question 2

A hospital autoclave is set to operate at 15 psi for 15 minutes. What is the primary reason large containers require longer sterilization times in an autoclave?

Accepted Answer

Steam must contact all surfaces, and heat penetration is slower in larger volumes.

Question 3

Which of the following statements about decimal reduction time ($$D_{RT}) is $$correct?

Accepted Answer

$$D_{RT} is $$the time required to kill 90\% of a microbial population at a given temperature.

Question 4

A solution contains $$1 	imes 10^6$ bacteria. If the decimal reduction time (D$$_{RT}$$) at a certain temperature is 2 minutes, how long will it take to reduce the population to 1$$ 	imes $$10^2$$ bacteria?

Accepted Answer

12 minutes

Question 5

Which of the following is NOT a factor that affects the effectiveness of a microbial control agent?

Accepted Answer

The color of the microbial cells

Question 6

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

Accepted Answer

Filtration

Question 7

Which of the following best explains why alcohol-based hand sanitizers are ineffective against Norovirus?

Accepted Answer

Norovirus is a nonenveloped virus, and alcohols are ineffective against nonenveloped viruses.

Question 8

Which chemical disinfectant is most likely to remain active in the presence of organic matter, such as blood or vomit?

Accepted Answer

Phenolics

Question 9

A laboratory technician is using the disk-diffusion method to test the effectiveness of several disinfectants. 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 statements about ionizing radiation is correct?

Accepted Answer

Ionizing radiation creates reactive hydroxyl radicals that damage DNA.

Question 11

Which of the following best describes the action of aldehydes as chemical disinfectants?

Accepted Answer

They inactivate proteins by cross-linking with functional groups.

Question 12

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 and is sporicidal.

Question 13

Which of the following is the primary mechanism by which high concentrations of salt or sugar preserve food?

Accepted Answer

They create a hypertonic environment, causing plasmolysis in microbial cells.

Question 14

A patient is treated with a skin antiseptic before surgery. Which halogen is most commonly used for this purpose, and what is its mechanism of action?

Accepted Answer

Iodine; impairs protein synthesis and alters membranes.

Question 15

Which of the following best explains why a can of pork takes longer to sterilize than a can of soup containing pieces of pork?

Accepted Answer

Heat penetrates solid pork more slowly than liquid soup, requiring longer sterilization times.

Question 16

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

Accepted Answer

It evaluates the effectiveness of disinfectants by exposing metal cylinders coated with bacteria to the disinfectant.

Question 17

Which of the following chemical food preservatives is primarily used to prevent endospore germination in meat products?

Accepted Answer

Nitrites and nitrates

Question 18

Which of the following statements about bacteriostasis is correct?

Accepted Answer

Bacteriostasis refers to inhibiting, but not killing, microbes.

Question 19

Which of the following is a gaseous chemosterilant used for sterilizing large pieces of equipment and heat-sensitive materials?

Accepted Answer

Ethylene oxide

Question 20

A researcher is using UV-C lamps to disinfect the surfaces in a hospital room. What is the primary limitation of this method?

Accepted Answer

UV-C radiation does not penetrate surfaces and is only effective for surface disinfection.

Chapter 7: The Control of Microbial Growth – Comprehensive Study Notes

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