Question 1

Which of the following best describes the mechanism by which high concentrations of salt or sugar preserve food?

Accepted Answer

They create a hypertonic environment, causing microbial cells to lose water.

Question 2

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

Accepted Answer

Filtration using a 0.22 μm membrane filter

Question 3

Which of the following statements about autoclaving is correct?

Accepted Answer

Autoclaving uses pressurized steam to achieve higher temperatures than boiling.

Question 4

Which of the following is the correct definition of 'thermal death point'?

Accepted Answer

The lowest temperature that kills all cells in a broth in 10 minutes.

Question 5

A laboratory is working with Ebola virus. Which biosafety level (BSL) is required, and why are the suits pressurized?

Accepted Answer

BSL-4; to prevent pathogens from entering the suit if it is punctured.

Question 6

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

Accepted Answer

Prions

Question 7

Why is moist heat generally more effective than dry heat for sterilization?

Accepted Answer

Moist heat denatures proteins and destroys membranes more efficiently.

Question 8

A batch of milk is treated at 72°C for 15 seconds. Which process is being used?

Accepted Answer

Flash pasteurization

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 the formation of ice crystals that damage microbial cells.

Question 10

Which of the following is NOT a factor affecting the efficacy of antimicrobial methods?

Accepted Answer

The color of the antimicrobial agent

Question 11

A solution is filtered through a membrane with a pore size of 0.22 μm. Which of the following will be removed?

Accepted Answer

Most bacteria and largest viruses

Question 12

Which term refers to the removal of all microorganisms and viruses on an object?

Accepted Answer

Sterilization

Question 13

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

Accepted Answer

Boiling is ineffective against endospores and some viruses.

Question 14

Which process is used for long-term preservation of microbial cultures by preventing the formation of damaging ice crystals?

Accepted Answer

Lyophilization

Question 15

A disinfectant is tested at two different temperatures: 20°C and 40°C. At which temperature would you expect the disinfectant to be more effective, and why?

Accepted Answer

40°C, because higher temperatures generally increase the efficacy of antimicrobial chemicals.

Question 16

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

Accepted Answer

The time required to reduce the microbial population by 90% at a given temperature.

Question 17

Which of the following is a correct statement about the action of antimicrobial agents on proteins and nucleic acids?

Accepted Answer

Damage to proteins can disrupt metabolism and structure, while damage to nucleic acids prevents correct protein synthesis.

Question 18

Which of the following is classified as a high-level germicide?

Accepted Answer

A chemical that kills all pathogens, including endospores

Question 19

Why are nonenveloped viruses generally more tolerant of harsh conditions than enveloped viruses?

Accepted Answer

Nonenveloped viruses lack a lipid membrane that can be disrupted by antimicrobial agents.

Controlling Microbial Growth in the Environment: Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards