Question 1

Which of the following best describes the mode of action of quaternary ammonium compounds (quats) as antimicrobial agents?

Accepted Answer

They disrupt cellular membranes, causing loss of essential ions.

Question 2

A hospital needs to sterilize heat-sensitive surgical instruments. Which method is most appropriate and why?

Accepted Answer

Gaseous ethylene oxide, because it sterilizes without heat and penetrates well.

Question 3

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

Accepted Answer

Microbial death rate is constant under a particular set of conditions and produces a straight line on a semilogarithmic graph.

Question 4

A batch of milk is pasteurized using the flash method. Which of the following best describes this process?

Accepted Answer

Heating at 72°C for 15 seconds.

Question 5

Why are Bacillus endospores used as sterility indicators in autoclaving?

Accepted Answer

They are exceptionally resistant to sterilization, so their destruction indicates effective sterilization.

Question 6

Which of the following is a limitation of using boiling as a method of microbial control?

Accepted Answer

Boiling is not effective against bacterial endospores and some viruses.

Question 7

A food processing plant wants to extend the shelf life of spices without making them radioactive. Which method should they use?

Accepted Answer

Gamma irradiation, because it kills microbes without making food radioactive.

Question 8

Which of the following best explains why nonenveloped viruses are more tolerant of harsh conditions than enveloped viruses?

Accepted Answer

Nonenveloped viruses have a protein capsid that is more resistant to desiccation and chemicals.

Question 9

A laboratory is working with a newly discovered virus that causes a fatal disease in humans and has no known treatment. Which biosafety level (BSL) is required for this work?

Accepted Answer

BSL-4

Question 10

Which of the following statements about the use of refrigeration for microbial control is correct?

Accepted Answer

Refrigeration slows microbial metabolism and growth, but some pathogens can still multiply.

Question 11

A patient develops food poisoning after eating raw cheese. The causative agent is identified as Campylobacter jejuni. Which of the following best explains why raw cheese is a likely source?

Accepted Answer

Campylobacter jejuni is a common foodborne pathogen linked to raw dairy products.

Question 12

Which of the following is a correct statement about the decimal reduction time (D value) in microbial control?

Accepted Answer

It is the time required to reduce a microbial population by 90% under specific conditions.

Question 13

Which of the following is a reason why moist heat is generally more effective than dry heat for sterilization?

Accepted Answer

Moist heat denatures proteins and destroys membranes more efficiently at lower temperatures.

Question 14

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

Accepted Answer

Filtration through a membrane filter with appropriate pore size.

Question 15

Which of the following best describes the effect of high concentrations of salt or sugar on microbial cells?

Accepted Answer

They create a hypertonic environment, causing cells to lose water and inhibiting growth.

Question 16

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

Accepted Answer

It is inactivated by catalase present in tissues, reducing its effectiveness.

Question 17

A researcher is working with Mycobacterium tuberculosis, which is transmitted via aerosols. Which biosafety level is required?

Accepted Answer

BSL-3

Question 18

Which of the following is a correct statement about the use of UV light for microbial control?

Accepted Answer

UV light causes pyrimidine dimers in DNA, inhibiting replication.

Question 19

A hospital is considering the use of phenolics for disinfecting surfaces. Which of the following is an advantage of phenolics?

Accepted Answer

They are effective in the presence of organic matter and remain active for prolonged periods.

Control of Microbial Growth: Principles, Methods, and Applications

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