Question 1

Which of the following statements best explains why ionizing radiation is effective at sterilizing medical equipment?

Accepted Answer

It ionizes water, forming highly reactive hydroxyl radicals that destroy cellular components.

Question 2

Which physical method of microbial control is most effective for disinfecting air and vaccines, and why?

Accepted Answer

Ultraviolet (UV) radiation, because it forms thymine dimers in DNA at 260 nm.

Question 3

A hospital is considering using a new disinfectant. Which of the following factors should NOT be a primary consideration when selecting the disinfectant?

Accepted Answer

The color of the disinfectant.

Question 4

Which of the following best describes the mechanism by which phenolics exert their antimicrobial action?

Accepted Answer

They disrupt plasma membranes, inactivate enzymes, and denature proteins.

Question 5

Why are Mycobacteria more susceptible to phenolics than other disinfectants?

Accepted Answer

Because phenolics can dissolve the high lipid content in their cell walls.

Question 6

Which of the following is a correct statement about the radiant energy spectrum?

Accepted Answer

Shorter wavelength radiation has more energy than longer wavelength radiation.

Question 7

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

Accepted Answer

The disinfectant is highly effective against the tested microbe.

Question 8

Which of the following is a reason why UV radiation is less effective for sterilizing thick or opaque materials?

Accepted Answer

UV radiation has a low degree of penetration.

Question 9

Which of the following microbes is generally most resistant to chemical disinfectants?

Accepted Answer

Prions

Question 10

Which of the following statements about bisphenols is correct?

Accepted Answer

Bisphenols contain two phenol molecules connected by a bridge and are effective against Staphylococci and Streptococci.

Question 11

Which of the following best explains why Pseudomonas aeruginosa is difficult to control with trichlosan?

Accepted Answer

It is very resistant to trichlosan due to its unique cell wall structure.

Question 12

Which of the following is NOT a principle of effective disinfection?

Accepted Answer

The color of the disinfectant.

Question 13

Which of the following is a correct application of ionizing radiation in food processing?

Accepted Answer

Low level ionizing radiation is used to process spices and certain meats and vegetables.

Question 14

Which of the following is the most effective germicidal wavelength for UV radiation?

Accepted Answer

$$260\ \mathrm{nm}$$

Question 15

Which of the following is a plausible reason why disinfectant activity is enhanced by warm temperatures?

Accepted Answer

Increased temperature increases the rate of chemical reactions, enhancing microbial killing.

Physical and Chemical Methods of Microbial Control

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