Question 1

Which of the following best defines sterilization in the context of microbial control?

Accepted Answer

The removal and destruction of all microbial life

Question 2

A hospital uses an autoclave to sterilize surgical instruments. What is the minimum standard condition for autoclaving to ensure sterilization (excluding prions)?

Accepted Answer

121°C at 15 psi for 15 minutes

Question 3

Which of the following statements about the decimal reduction time ($$D_{10}) is $$correct?

Accepted Answer

$$D_{10} is $$the time (in minutes) required to kill 90\% of a specific population of bacteria at a given temperature.

Question 4

A laboratory technician needs to sterilize a heat-sensitive vitamin solution. Which method is most appropriate?

Accepted Answer

Membrane filtration

Question 5

Which of the following is a correct example of antisepsis?

Accepted Answer

Cleaning a surgical wound with povidone-iodine

Question 6

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

Accepted Answer

Their outer membrane contains lipopolysaccharide, which restricts entry of biocides.

Question 7

Which of the following chemical agents is most effective for sterilizing heat-sensitive medical equipment such as endoscopes?

Accepted Answer

Glutaraldehyde

Question 8

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

Accepted Answer

Nitrites

Question 9

Which physical method of microbial control is most effective for sterilizing disposable plastic syringes?

Accepted Answer

Ionizing radiation (gamma rays)

Question 10

Which of the following statements about alcohol-based hand sanitizers is correct?

Accepted Answer

They require water to be effective and are not effective against Clostridium difficile.

Question 11

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

Accepted Answer

The disinfectant is highly effective against the test organism.

Question 12

Which of the following best describes the action of chlorine as a disinfectant?

Accepted Answer

It oxidizes cellular components, shutting down enzyme systems.

Question 13

Which of the following is a limitation of using hydrogen peroxide as an antiseptic for open wounds?

Accepted Answer

It is rapidly broken down by catalase in tissues, reducing its effectiveness.

Question 14

Which of the following statements about prions is correct?

Accepted Answer

They are inactivated by immersion in NaOH followed by autoclaving at 121°C for 1 hour.

Question 15

Which of the following is a correct example of sanitization?

Accepted Answer

Lowering microbial counts on eating utensils to safe levels

Question 16

Which of the following best explains why moist heat is generally more effective than dry heat for sterilization?

Accepted Answer

Moist heat denatures proteins more rapidly due to better heat transfer.

Question 17

A patient with a catheter is at risk for infection due to biofilm formation. Which environmental factor most contributes to the resistance of biofilms to disinfectants?

Accepted Answer

Protective extracellular matrix limiting disinfectant penetration

Question 18

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

Accepted Answer

It is one of the few liquid chemical sterilizing agents (sporicidal in 3–10 hours).

Question 19

Which of the following best describes the mechanism of action of nonionizing radiation (UV light) in microbial control?

Accepted Answer

It creates thymine dimers in DNA, leading to lethal mutations.

Question 20

A hospital is considering using gaseous chemosterilants for sterilizing large pieces of equipment. Which of the following is a gaseous chemosterilant that acts by alkylation?

Accepted Answer

Ethylene oxide

The Control of Microbial Growth: Principles and Methods

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