$$D = \text{minutes to kill } 90\% \text{ of a specific population at a given temperature}$$

Question 1

Which of the following best describes the process of commercial sterilization in the food industry?

Accepted Answer

Killing Clostridium botulinum endospores in canned goods to prevent botulism

Question 2

A hospital uses an autoclave to sterilize surgical instruments. What are the standard conditions required for effective autoclaving?

Accepted Answer

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

Question 3

Which term refers to the mechanical removal of microbes from a limited area, such as when preparing a patient’s skin for injection?

Accepted Answer

Degerming

Question 4

A food processing plant wants to reduce spoilage organisms and pathogens in milk without sterilizing it. Which method should they use?

Accepted Answer

Pasteurization

Question 5

Which of the following statements about bacteriostasis is correct?

Accepted Answer

It inhibits the growth of bacteria without killing them

Question 6

A researcher is testing the effectiveness of a new disinfectant using the disk-diffusion method. What result indicates the disinfectant is effective?

Accepted Answer

A large zone of inhibition around the disk

Question 7

Which physical method of microbial control is most appropriate for sterilizing heat-sensitive liquids such as vaccines?

Accepted Answer

Filtration

Question 8

Which chemical agent is sporicidal and commonly used to sterilize medical equipment that cannot be autoclaved?

Accepted Answer

Glutaraldehyde

Question 9

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

Accepted Answer

They possess lipopolysaccharide in their outer membrane

Question 10

Which of the following is the correct definition of thermal death point (TDP)?

Accepted Answer

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

Question 11

A nurse uses an alcohol-based hand sanitizer. Which type of microorganism is LEAST likely to be killed by this sanitizer?

Accepted Answer

Nonenveloped viruses

Question 12

Which chemical food preservative is primarily used to prevent endospore germination in meat products?

Accepted Answer

Nitrites

Question 13

Which physical method of microbial control works by creating a hypertonic environment that causes plasmolysis?

Accepted Answer

Osmotic pressure

Question 14

Which type of radiation is most effective for sterilizing pharmaceuticals and disposable medical supplies due to its deep penetration?

Accepted Answer

Gamma rays

Question 15

A hospital uses UVC lamps to disinfect surfaces in operating rooms. What is the primary mechanism by which UVC kills microbes?

Accepted Answer

Creation of thymine dimers in DNA

Question 16

Which of the following factors does NOT directly affect the rate of microbial death when using control agents?

Accepted Answer

Color of the microbial colony

Question 17

A dentist uses glutaraldehyde to sterilize equipment. What is a major advantage of glutaraldehyde over other chemical disinfectants?

Accepted Answer

It is sporicidal and can sterilize in 3-10 hours

Question 18

Which of the following equations represents the decimal reduction time (DRT) in microbial control?

Accepted Answer

$$D = 	ext{minutes to kill } 90\% 	ext{ of a specific population at a given temperature}$$

Question 19

Which chemical agent is used in water treatment and acts as an oxidizing agent to shut down cellular enzyme systems?

Accepted Answer

Chlorine

Question 20

A patient develops a skin infection caused by staphylococci. Which bisphenol compound is most likely used to prevent or control this infection?

Accepted Answer

Hexachlorophene

Control of Microbial Growth: Key Concepts and Terminology

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