Question 1

Which of the following best describes the difference between sterilization and disinfection?

Accepted Answer

Sterilization removes all microbes, including endospores, while disinfection only reduces the number of pathogens and may not affect endospores.

Question 2

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

Accepted Answer

Gaseous agents such as ethylene oxide

Question 3

Which of the following statements about autoclaving is correct?

Accepted Answer

Autoclaving uses moist heat at 121ºC and 15 psi for at least 15 minutes to achieve sterilization.

Question 4

Which physical method of microbial control is most effective for sterilizing heat-sensitive solutions such as vaccines?

Accepted Answer

Filtration

Question 5

Why is moist heat generally more effective than dry heat for microbial control?

Accepted Answer

Water is a better conductor of heat than air, allowing proteins to denature more rapidly.

Question 6

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

Accepted Answer

Boiling does not reliably kill endospores or some viruses.

Question 7

A laboratory is working with a newly discovered virus that causes fatal disease in humans. Which biosafety level (BSL) is required?

Accepted Answer

Biosafety Level 4 (BSL-4)

Question 8

Which chemical agent is most appropriate for disinfecting water in a municipal treatment plant?

Accepted Answer

Chlorine

Question 9

Which of the following best explains why milk can still spoil even after pasteurization?

Accepted Answer

Pasteurization does not sterilize; heat-tolerant microbes may survive.

Question 10

Which of the following is the main mechanism of action for alcohols as antimicrobial agents?

Accepted Answer

Denaturation of proteins and disruption of cytoplasmic membranes

Question 11

A food manufacturer wants to preserve fruit jam for long-term storage at room temperature. Which method is most effective?

Accepted Answer

Osmotic pressure using high sugar concentration

Question 12

Which of the following statements about ionizing radiation is correct?

Accepted Answer

Ionizing radiation creates ions that disrupt hydrogen bonding and denature DNA.

Question 13

Which of the following is a disadvantage of using gaseous agents such as ethylene oxide for sterilization?

Accepted Answer

They are potentially carcinogenic and highly explosive.

Question 14

Which of the following best describes the action of heavy metals as antimicrobial agents?

Accepted Answer

They denature proteins, resulting in bacteriostatic and fungistatic effects.

Question 15

A researcher needs to preserve a bacterial culture for several years. Which method is most appropriate?

Accepted Answer

Lyophilization

Question 16

Which of the following is a reason why the use of antiseptic and disinfectant chemicals can promote the development of resistant microbes?

Accepted Answer

Frequent exposure to sublethal concentrations selects for resistant strains.

Question 17

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

Accepted Answer

Slow freezing allows ice crystals to form and puncture cell membranes.

Question 18

Which of the following is a correct statement about the use of surfactants in microbial control?

Accepted Answer

Surfactants reduce surface tension and disrupt cell membranes, aiding in degerming.

Question 19

Which method would be most appropriate for sterilizing a solution of antibiotics that cannot withstand heat?

Accepted Answer

Filtration through a membrane with appropriate pore size

Question 20

Which of the following is the main mechanism by which aldehydes such as glutaraldehyde act as antimicrobial agents?

Accepted Answer

Cross-linking functional groups to denature proteins and inactivate nucleic acids

Controlling Microbial Growth in the Environment: Physical and Chemical Methods

Study Guide - Practice Questions