Question 1

Which of the following best describes the decimal reduction time (DRT) in microbial control?

Accepted Answer

The time required to kill 90% of a specific population of bacteria at a given temperature.

Question 2

A hospital technician needs to sterilize a 2000 mL Erlenmeyer flask containing a liquid medium. According to the provided data, what is the minimum recommended autoclave time at 121°C and 15 psi?

Accepted Answer

$$35$$ minutes

Question 3

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

Accepted Answer

When plotted logarithmically, the microbial death curve is a straight line.

Question 4

Which physical method is most appropriate for sterilizing heat-sensitive solutions such as antibiotics or vaccines?

Accepted Answer

Filtration through a $$0.22\ \mu\mathrm{m}$$ membrane

Question 5

Which of the following chemical agents is most effective against both endospores and mycobacteria?

Accepted Answer

Glutaraldehyde

Question 6

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

Accepted Answer

A large zone of inhibition around the disk

Question 7

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

Accepted Answer

Water is required for protein denaturation, which is essential for ethanol's antimicrobial action.

Question 8

Which of the following is NOT a correct match between the agent and its primary mode of action?

Accepted Answer

Heavy metals – Inhibit DNA replication

Question 9

A laboratory is using a HEPA filter to sterilize air entering a clean room. What is the minimum particle size that will be removed by this filter?

Accepted Answer

$$0.3\ \mu\mathrm{m}$$

Question 10

Which of the following statements about autoclaving is FALSE?

Accepted Answer

Autoclaving destroys all exotoxins and endotoxins.

Question 11

Which of the following best describes the effect of high osmotic pressure on microbial cells?

Accepted Answer

It causes plasmolysis by drawing water out of the cell.

Question 12

Which of the following is a correct application of the use-dilution test?

Accepted Answer

Evaluating the efficacy of chemical disinfectants by measuring bacterial survival on metal cylinders.

Question 13

Which of the following statements about pasteurization is TRUE?

Accepted Answer

It reduces spoilage organisms and pathogens using high temperature for a short time.

Question 14

Which of the following is the primary reason why larger containers require longer autoclave sterilization times?

Accepted Answer

It takes longer for the contents to reach the sterilization temperature.

Question 15

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

Accepted Answer

They are not effective against endospores and nonenveloped viruses.

Question 16

Which of the following best explains why nonionizing radiation (UV light) is effective at controlling microbial growth?

Accepted Answer

It damages DNA by creating thymine dimers.

Question 17

A food manufacturer wants to prevent the growth of molds in acidic foods. Which of the following preservatives would be most appropriate?

Accepted Answer

Sorbic acid

Question 18

Which of the following is the best definition of asepsis?

Accepted Answer

The absence of significant microbial contamination.

Question 19

Which of the following statements about quaternary ammonium compounds (quats) is TRUE?

Accepted Answer

They denature proteins and disrupt plasma membranes.

Question 20

A patient is treated with silver nitrate to prevent ophthalmia neonatorum. What is the primary antimicrobial mechanism of silver nitrate?

Accepted Answer

Denaturation of proteins

Control of Microbial Growth: Principles, Methods, and Applications

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