Question 1

Which of the following best describes the mechanism by which moist heat kills microorganisms?

Accepted Answer

It denatures proteins and destroys cytoplasmic membranes.

Question 2

A hospital needs to sterilize heat-sensitive plastic syringes. Which method is most appropriate?

Accepted Answer

Gaseous ethylene oxide treatment

Question 3

Which of the following statements about the decimal reduction time (D-value) is correct?

Accepted Answer

It is the time required to reduce a microbial population by 90% at a specific temperature.

Question 4

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 positive pressure suits and isolated facilities

Question 5

Which of the following is a limitation of using hydrogen peroxide as an antiseptic for open wounds?

Accepted Answer

It is neutralized by catalase present in tissues.

Question 6

A food company wants to preserve fruit jam. Which physical method is most effective for inhibiting microbial growth in this product?

Accepted Answer

High osmotic pressure using sugar

Question 7

Which of the following chemical agents is most effective for sterilizing medical equipment contaminated with endospores?

Accepted Answer

Glutaraldehyde

Question 8

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

Accepted Answer

They lack a lipid envelope that is easily disrupted by chemicals.

Question 9

Which of the following best explains why slow freezing is more effective than quick freezing for microbial control?

Accepted Answer

Slow freezing causes formation of ice crystals that damage cell structures.

Question 10

A laboratory technician is asked to sterilize a solution that contains heat-sensitive vitamins. Which method should be used?

Accepted Answer

Membrane filtration

Question 11

Which of the following statements about phenol coefficient is correct?

Accepted Answer

It compares the effectiveness of a disinfectant to phenol.

Question 12

Which of the following is a real-world example of degerming?

Accepted Answer

Washing hands with soap and water

Question 13

Which of the following best describes the action of surfactants such as quaternary ammonium compounds?

Accepted Answer

They disrupt cellular membranes by reducing surface tension.

Question 14

Which physical method is most suitable for long-term preservation of microbial cultures?

Accepted Answer

Lyophilization

Question 15

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

Accepted Answer

They can be hazardous, explosive, and potentially carcinogenic.

Question 16

Which of the following best explains why UV light is only suitable for disinfecting air, transparent fluids, and surfaces?

Accepted Answer

UV light does not penetrate well through solids or opaque liquids.

Question 17

A nurse prepares a patient’s skin with iodine before an injection. This is an example of which microbial control term?

Accepted Answer

Antisepsis

Question 18

Which of the following is the primary reason why autoclaving is more effective than boiling for sterilization?

Accepted Answer

Autoclaving uses higher temperatures and pressure to kill endospores.

Question 19

Which of the following best describes the effect of ionizing radiation on microbial cells?

Accepted Answer

It ejects electrons, creating ions that disrupt DNA and proteins.

Question 20

A laboratory is testing a new disinfectant using the use-dilution test. Which result indicates the disinfectant is effective?

Accepted Answer

No bacterial growth is observed at the highest dilution.

Controlling Microbial Growth in the Environment

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