Question 1

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

Accepted Answer

Sterilization destroys all microbial life, while disinfection reduces or destroys harmful microorganisms on inanimate surfaces.

Question 2

A hospital is preparing surgical instruments for use. Which method should be used to ensure all forms of microbial life, including endospores, are destroyed?

Accepted Answer

Autoclaving at $$121^{\circ}C $$and 15 psi for 15 minutes

Question 3

Which of the following statements about the rate of microbial death is correct?

Accepted Answer

The rate of microbial death is logarithmic, meaning a constant proportion of cells die per unit time.

Question 4

A researcher 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 definition of the thermal death point (TDP)?

Accepted Answer

The lowest temperature at which all cells in a liquid culture are killed in 10 minutes

Question 6

Which chemical agent is most effective for skin antisepsis before surgery and works by disrupting plasma membranes?

Accepted Answer

Chlorhexidine (a biguanide)

Question 7

A food processing plant wants to prevent the growth of Clostridium botulinum in canned goods. What process should be used?

Accepted Answer

Commercial sterilization

Question 8

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

Accepted Answer

They are not effective against endospore-forming bacteria and nonenveloped viruses.

Question 9

A laboratory is testing the effectiveness of a new disinfectant using the dilution test. What is the correct sequence of steps?

Accepted Answer

Dip metal cylinders in test bacteria, dry, expose to disinfectant, then transfer to culture media.

Question 10

Which of the following best explains why large containers require longer autoclave sterilization times?

Accepted Answer

It takes longer for heat to penetrate and reach all parts of the larger volume.

Question 11

Which of the following physical methods of microbial control is most effective for removing airborne particles, such as dust and pollen, from hospital air?

Accepted Answer

High-efficiency particulate air (HEPA) filtration

Question 12

Which of the following statements about ionizing and nonionizing radiation is correct?

Accepted Answer

Ionizing radiation causes lethal mutations in DNA, while nonionizing radiation creates thymine dimers.

Question 13

A patient with a wound infection is treated with a silver-impregnated dressing. What is the primary antimicrobial mechanism of silver?

Accepted Answer

Denaturation of proteins via oligodynamic action

Question 14

Which of the following best describes the action of phenolic compounds such as O-phenylphenol?

Accepted Answer

They injure lipids in plasma membranes, causing leakage of cellular contents.

Question 15

A microbiologist is using the disk-diffusion method to test a new antiseptic. What result indicates the antiseptic is effective?

Accepted Answer

A clear zone of inhibition around the disk

Question 16

Which of the following is a limitation of using alcohols as disinfectants?

Accepted Answer

They are not effective against endospores and nonenveloped viruses.

Question 17

A laboratory is using UV-C lamps to sterilize surfaces. What is the primary mechanism by which UV-C radiation kills microbes?

Accepted Answer

Formation of thymine dimers in DNA

Question 18

Which of the following best explains why high concentrations of salt or sugar can preserve food?

Accepted Answer

They create a hypertonic environment, causing plasmolysis in microbes.

Question 19

A scientist is evaluating a new gaseous sterilant for use on heat-sensitive medical equipment. Which of the following is a common gaseous sterilant that cross-links nucleic acids and proteins?

Accepted Answer

Ethylene oxide

Question 20

Which of the following best describes the action of aldehydes such as formalin in microbial control?

Accepted Answer

They inactivate proteins by cross-linking with functional groups.

Control of Microbial Growth: Principles and Methods

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