Question 1

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

Accepted Answer

Sterilization destroys all microorganisms and viruses on an object, while disinfection eliminates most pathogens but not all microbes or endospores.

Question 2

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

Accepted Answer

Sterilization

Question 3

Which of the following is the most resistant to antimicrobial agents?

Accepted Answer

Prions

Question 4

A solution is described as bacteriostatic. What does this imply about its effect on bacteria?

Accepted Answer

It inhibits the growth and reproduction of bacteria without killing them.

Question 5

Which of the following best explains why 70% alcohol is more effective as an antimicrobial agent than 100% alcohol?

Accepted Answer

Water is required for protein denaturation, so 70% alcohol penetrates cells better and denatures proteins more effectively.

Question 6

A laboratory is using an autoclave to sterilize media. The standard conditions are 121°C at 15 psi for 15 minutes. What is the primary advantage of using moist heat in an autoclave compared to dry heat in an oven?

Accepted Answer

Moist heat denatures proteins and destroys membranes more rapidly, requiring lower temperatures and shorter times than dry heat.

Question 7

Which of the following equations correctly represents the decimal reduction time (D-value) in microbial control?

Accepted Answer

$$D = \frac{t}{\log_{10}(N_0$/N)}$$

Question 8

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

Accepted Answer

Filtration

Question 9

Why are nonenveloped viruses generally more resistant to harsh environmental conditions than enveloped viruses?

Accepted Answer

Nonenveloped viruses lack a lipid envelope, making them less susceptible to agents that disrupt membranes.

Question 10

Which of the following best describes the action of surfactants in microbial control?

Accepted Answer

They reduce surface tension of solvents, making it easier to remove microbes from surfaces.

Question 11

A food processing plant wants to extend the shelf life of strawberries without using heat. Which method would be most effective?

Accepted Answer

Ionizing radiation

Question 12

Which biosafety level (BSL) is required for handling Ebola virus, and what is a key feature of this level?

Accepted Answer

BSL-4; use of full-body, air-supplied suits and isolated facilities

Question 13

Which of the following statements about the use-dilution test is correct?

Accepted Answer

It evaluates disinfectant effectiveness by immersing contaminated cylinders into different dilutions and observing microbial growth.

Question 14

Which of the following is a disadvantage of using gaseous agents for microbial control?

Accepted Answer

They can be hazardous, explosive, and potentially carcinogenic.

Question 15

A laboratory technician is preparing a solution for use as an antiseptic on human skin. Which of the following would be most appropriate?

Accepted Answer

70% isopropyl alcohol

Question 16

Which of the following best explains why organic materials can interfere with the effectiveness of chemical disinfectants?

Accepted Answer

Organic materials can inactivate chemical disinfectants and block their penetration.

Question 17

Which of the following is the correct order of microbial resistance from most resistant to most susceptible?

Accepted Answer

Prions \u003e Bacterial endospores \u003e Enveloped viruses

Question 18

Which of the following statements about pasteurization is correct?

Accepted Answer

Pasteurization reduces the number of pathogens and spoilage organisms without sterilizing the product.

Question 19

Which chemical agent is used to remove prions from medical instruments?

Accepted Answer

Prionzyme

Question 20

A solution contains 1% silver nitrate. What is its primary use in microbial control?

Accepted Answer

Preventing blindness caused by Neisseria gonorrhoeae in newborns

Ch 9 - Controlling Microbial Growth in the Environment

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