Question 1

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

Accepted Answer

Sterilization destroys all microorganisms and viruses, while disinfection only destroys most pathogens on nonliving tissue.

Question 2

A hospital wants to sterilize heat-sensitive medical equipment. Which method is most appropriate?

Accepted Answer

Gaseous ethylene oxide sterilization

Question 3

Which of the following is the correct equation for calculating the decimal reduction time (D-value) in microbial death rate studies?

Accepted Answer

$$D = \frac{t}{\log_{10}(N_0$) - \log_{10}(N)}$$

Question 4

Why are Bacillus endospores used as sterility indicators in autoclaving?

Accepted Answer

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

Question 5

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

Accepted Answer

Filtration using a membrane filter with pore size $$0.22\ \mu m$$

Question 6

A food processing plant wants to extend the shelf life of packaged fruit juice without altering its taste or nutrients. Which method should they use?

Accepted Answer

Ultra-high-temperature (UHT) sterilization at $$140^\circ C$$ for 1–3 seconds

Question 7

Which of the following statements about the use of antimicrobial soaps in households is most accurate based on current recommendations?

Accepted Answer

Regular soap and water are sufficient for most situations; antimicrobial soaps are usually unnecessary.

Question 8

Which of the following is the primary mode of action for alcohols as disinfectants?

Accepted Answer

Denaturation of proteins and disruption of cytoplasmic membranes

Question 9

A laboratory is working with Ebola virus. Which biosafety level (BSL) is required?

Accepted Answer

BSL-4

Question 10

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

Accepted Answer

They lack a lipid envelope, making them less susceptible to agents that disrupt membranes.

Question 11

A patient develops food poisoning after eating raw cheese. The causative agent is identified as Campylobacter jejuni. Which control method would have prevented this infection?

Accepted Answer

Pasteurization of the milk used to make the cheese

Question 12

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

Accepted Answer

It is highly explosive and potentially carcinogenic.

Question 13

Which of the following methods is most suitable for long-term preservation of microbial cultures?

Accepted Answer

Lyophilization (freeze-drying)

Question 14

Which chemical agent is commonly used to disinfect water in municipal treatment plants?

Accepted Answer

Chlorine

Question 15

Which of the following best describes the effect of high osmotic pressure (e.g., salting or sugaring) on microbial cells?

Accepted Answer

Cells lose water and metabolism is inhibited.

Question 16

Which of the following is the main reason why UV light is not suitable for sterilizing large volumes of liquid?

Accepted Answer

UV light does not penetrate well through liquids.

Question 17

A microbiologist needs to sterilize a glass pipette. Which method is most appropriate?

Accepted Answer

Incineration

Question 18

Which of the following is a correct statement about the effect of temperature on the efficacy of antimicrobial chemicals?

Accepted Answer

Higher temperatures generally increase the efficacy of antimicrobial chemicals.

Question 19

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

Accepted Answer

Catalase in tissues breaks down hydrogen peroxide, reducing its effectiveness.

Question 20

Which of the following best explains why a little dirt and exposure to pets may be beneficial for children’s immune development?

Accepted Answer

Exposure to diverse microbes helps train and strengthen the immune system.

Control of Microbial Growth: Principles, Methods, and Applications

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