Question 1

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

Accepted Answer

Sterilization destroys all forms of microbial life, including endospores, while disinfection eliminates only vegetative pathogens but not endospores.

Question 2

A hospital wants to sterilize heat-sensitive plastic syringes. Which method would be most appropriate?

Accepted Answer

Ethylene oxide gas sterilization

Question 3

Which of the following is the correct chemical equation for the formation of hypochlorous acid when chlorine is added to water?

Accepted Answer

$$\mathrm{Cl_2$ + H_2O \rightarrow H^+ + Cl^- + HOCl}$$

Question 4

Which of the following microbial forms is MOST resistant to chemical and physical control methods?

Accepted Answer

Prions

Question 5

A laboratory technician needs to sterilize a solution that cannot withstand heat. Which method should be used?

Accepted Answer

Membrane filtration with pore size $$0.22\ \mu m$$

Question 6

Which of the following best explains why 70% ethanol is more effective as a disinfectant than 100% ethanol?

Accepted Answer

Water is required for protein denaturation, which is the main mechanism of action for ethanol.

Question 7

Which physical method of microbial control is most likely to cause thymine dimers in DNA?

Accepted Answer

Ultraviolet (UV) radiation

Question 8

A food processing plant wants to reduce microbial contamination in fruit juices without altering their flavor. Which method is most suitable?

Accepted Answer

Membrane filtration

Question 9

Which of the following statements about phenolic compounds (such as those in Lysol) is TRUE?

Accepted Answer

They disrupt plasma membranes and denature proteins, and are effective even in the presence of organic matter.

Question 10

Which of the following is a disadvantage of using ionizing radiation for sterilization?

Accepted Answer

It may cause genetic mutations in humans due to its ability to penetrate tissues.

Question 11

Which of the following is the most appropriate use of glutaraldehyde in a hospital setting?

Accepted Answer

Sterilizing heat-sensitive medical instruments

Question 12

Which of the following best describes the mechanism of action of hydrogen peroxide as a disinfectant?

Accepted Answer

It acts as an oxidizing agent, damaging cellular components and disrupting membranes.

Question 13

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

Accepted Answer

Degerming

Question 14

Which of the following factors does NOT directly affect the effectiveness of an antimicrobial treatment?

Accepted Answer

The color of the microbial cells

Question 15

Which of the following is a limitation of using UV radiation for disinfection?

Accepted Answer

It does not penetrate paper, glass, or cloth.

Question 16

Which of the following best explains why bacterial endospores are more resistant to chemical disinfectants than vegetative cells?

Accepted Answer

Endospores have a tough, protective outer coat and low metabolic activity.

Question 17

Which of the following is a correct statement about the use of aldehydes as disinfectants?

Accepted Answer

They inactivate proteins by forming covalent crosslinks with functional groups.

Question 18

A microbiologist is evaluating a new disinfectant using the disk-diffusion method. What does a larger zone of inhibition indicate?

Accepted Answer

Greater effectiveness of the disinfectant against the tested microbe

Question 19

Which of the following is a reason why prions are the most resistant to physical and chemical control methods?

Accepted Answer

They lack nucleic acids and are composed solely of misfolded proteins.

Question 20

Which of the following statements about the use of surfactants (such as soaps and detergents) in microbial control is TRUE?

Accepted Answer

Cationic detergents are more effective than anionic detergents because they bind well to negatively charged bacterial surfaces.

Physical and Chemical Controls of Microorganisms: Microbiology Study Guide

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