Question 1

Which of the following statements 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 pathogens and does not eliminate endospores.

Question 2

A hospital is deciding how to sterilize a batch of heat-sensitive plastic syringes. Which method would be most appropriate?

Accepted Answer

Ethylene oxide gas sterilization

Question 3

Which of the following best defines decimal reduction time (DRT)?

Accepted Answer

The time in minutes required to kill 90% of a microbial population at a given temperature

Question 4

A food processing plant is concerned about Clostridium botulinum spores in canned vegetables. Which process is specifically designed to address this risk?

Accepted Answer

Commercial sterilization

Question 5

Which of the following is the correct order of microbial resistance to physical and chemical control methods, from least to most resistant?

Accepted Answer

Enveloped viruses \u003c Gram-positive bacteria \u003c Protozoan cysts \u003c Bacterial endospores \u003c Prions

Question 6

A laboratory technician is preparing a heat-sensitive vitamin solution for sterile use. Which method should be used to sterilize this solution?

Accepted Answer

Filtration through a $$0.22\ \mu m$$ membrane filter

Question 7

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

Accepted Answer

It measures the effectiveness of disinfectants by exposing stainless steel cylinders coated with test organisms to the chemical and then assessing microbial survival.

Question 8

Which of the following best explains why 70% ethanol is more effective as a disinfectant than 95% ethanol?

Accepted Answer

Water in 70% ethanol slows protein coagulation, allowing deeper penetration and more effective denaturation of proteins.

Question 9

A patient receives a wound dressing containing silver. What is the primary mechanism by which silver acts as an antimicrobial agent?

Accepted Answer

It alters the three-dimensional shape of proteins, interfering with their function.

Question 10

Which of the following food preservation methods is most effective at eliminating parasites and bacteria, but not viruses or prions, from food products?

Accepted Answer

Ionizing radiation (irradiation)

Question 11

A microbiologist is using the disk-diffusion method to test a new disinfectant. What does the 'zone of inhibition' represent?

Accepted Answer

The area around the disk where bacterial growth is prevented due to the chemical's effectiveness

Question 12

Which of the following statements about autoclaving is correct?

Accepted Answer

Autoclaving uses steam under pressure at $$121^\circ C$$ and 15 psi to achieve sterilization.

Question 13

Which of the following is a limitation of using ultraviolet (UV) light for disinfection?

Accepted Answer

UV light has poor penetration and is only effective on surfaces or transparent fluids.

Question 14

A nurse cleans a patient's skin with alcohol before giving an injection. This process is best described as:

Accepted Answer

Degermination

Question 15

Which of the following best describes the effect of osmotic pressure in food preservation?

Accepted Answer

High concentrations of salt or sugar cause plasmolysis, inhibiting microbial growth.

Question 16

Which of the following is a disadvantage of using aldehydes such as glutaraldehyde for disinfection?

Accepted Answer

Prolonged exposure may be required and they can be irritating or toxic to tissues.

Question 17

A batch of milk is processed at $$138^\circ C$$ for a fraction of a second and then packaged for storage at room temperature. Which process is being used?

Accepted Answer

Ultrahigh temperature (UHT) pasteurization

Question 18

Which of the following factors does NOT increase the effectiveness of a chemical disinfectant?

Accepted Answer

Presence of organic matter such as blood or feces

Question 19

A hospital is evaluating two disinfectants using the disk-diffusion method. Disinfectant A produces a larger zone of inhibition than Disinfectant B against Staphylococcus aureus. What can be concluded?

Accepted Answer

Disinfectant A is more effective against Staphylococcus aureus under the test conditions.

Question 20

Which of the following statements about food irradiation is correct?

Accepted Answer

Irradiation does not make food radioactive and is effective at eliminating parasites and bacteria.

Controlling Microbial Growth: Physical and Chemical Methods

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