Question 1

Which of the following best describes the difference between sterilization and disinfection?

Accepted Answer

Sterilization eliminates all forms of microbial life, including endospores and prions, while disinfection destroys only vegetative microbes and does not affect endospores.

Question 2

A hospital needs to sterilize heat-sensitive plastic instruments. Which method is most appropriate?

Accepted Answer

Ethylene oxide gas sterilization

Question 3

Which of the following organisms is most resistant to antimicrobial treatment?

Accepted Answer

Prions

Question 4

A solution is treated at 121ºC under 15 psi pressure for 20 minutes. What process is being used?

Accepted Answer

Autoclaving

Question 5

Which of the following statements about pasteurization is correct?

Accepted Answer

Pasteurization reduces the number of viable pathogens but does not sterilize the product.

Question 6

A laboratory technician needs to sterilize a heat-sensitive vitamin solution. Which method should be used?

Accepted Answer

Filtration through a 0.22 μm membrane

Question 7

Which of the following is a disadvantage of using phenolic compounds for disinfection?

Accepted Answer

They can irritate skin and mucous membranes and have an intense odor.

Question 8

Which physical method of microbial control is most effective for sterilizing inoculating loops in a laboratory?

Accepted Answer

Direct flaming (incineration)

Question 9

A food company wants to preserve fruit juice so it can be stored at room temperature for months. Which method should they use?

Accepted Answer

Ultra-high temperature (UHT) pasteurization

Question 10

Which of the following best explains why boiling is not a reliable method for sterilization?

Accepted Answer

Boiling does not destroy bacterial endospores and prions.

Question 11

Which chemical agent is most effective as a disinfectant in the presence of organic matter such as vomit or feces?

Accepted Answer

Phenolics

Question 12

A researcher wants to compare the effectiveness of several disinfectants. Which method should they use?

Accepted Answer

Disk-diffusion test

Question 13

Which of the following statements about the exponential death of microbes is correct?

Accepted Answer

A one-log decrease means 90% of the microbial population is killed.

Question 14

Which of the following is a limitation of using quaternary ammonium compounds (quats) for microbial control?

Accepted Answer

They are ineffective against naked viruses, mycobacteria, and endospores.

Question 15

Which of the following best describes the mechanism by which ionizing radiation controls microbial growth?

Accepted Answer

It causes DNA damage, leading to mutations and cell death.

Question 16

A nurse wipes a patient's skin with alcohol before an injection. This is an example of which process?

Accepted Answer

Degermination

Question 17

Which of the following is a reason why refrigeration is considered bacteriostatic rather than bactericidal?

Accepted Answer

It halts the growth of many pathogens but does not kill them.

Question 18

Which of the following is a practical advantage of dry heat sterilization over moist heat sterilization?

Accepted Answer

It can be used on powders and heat-stable objects that would be damaged by steam.

Question 19

Which of the following best explains why high concentrations of salt or sugar are used in food preservation?

Accepted Answer

They create a hypertonic environment, causing water to leave microbial cells and inhibiting growth.

Question 20

A patient receives a burn cream containing silver. What is the role of silver in this context?

Accepted Answer

It acts as a heavy metal that interferes with microbial protein function.

Physical and Chemical Methods of Microbial Control

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