Question 1

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

Accepted Answer

Sterilization removes all forms of microbial life, including spores, while disinfection eliminates only vegetative pathogens but not spores.

Question 2

A hospital is preparing surgical instruments for use. Which of the following methods would ensure complete removal of all microbial life, including endospores?

Accepted Answer

Autoclaving at $$121^\circ C$$ for 15 minutes at 15 psi

Question 3

Which of the following is the correct definition of decimal reduction time ($$D-$$value)?

Accepted Answer

The time required to kill $$90\% of a $$microbial population at a given temperature

Question 4

Which of the following factors does NOT affect the rate of microbial death during disinfection?

Accepted Answer

The color of the microbial cells

Question 5

A batch of milk is pasteurized using the high-temperature, short-time (HTST) method. What are the standard conditions for this process?

Accepted Answer

$$72^\circ C$$ for 15 seconds

Question 6

Which of the following pathogens is specifically targeted by milk pasteurization to prevent transmission?

Accepted Answer

Mycobacterium tuberculosis

Question 7

Which of the following is a correct statement about the effectiveness of filtration as a microbial control method?

Accepted Answer

Filtration is effective for removing bacteria from heat-sensitive liquids but does not remove viruses unless pore size is very small.

Question 8

Which of the following best explains why $$70\%$$ isopropyl alcohol is more effective as a disinfectant than $$100\%$$ isopropyl alcohol?

Accepted Answer

Water assists in protein denaturation and slows evaporation, increasing contact time.

Question 9

Which of the following chemical agents is classified as a high-level disinfectant and is considered a chemical sterilant?

Accepted Answer

Glutaraldehyde

Question 10

A hospital is considering the use of ethylene oxide ($$\mathrm{EtO}) $$gas for sterilization. Which of the following is a significant disadvantage of this method?

Accepted Answer

Ethylene oxide is toxic and requires lengthy aeration to remove residues.

Question 11

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

Accepted Answer

They are cationic detergents that disrupt cell membranes and are effective against many bacteria and enveloped viruses.

Question 12

Which of the following is a mechanism of action for hydrogen peroxide gas plasma sterilization?

Accepted Answer

Generation of free radicals that damage cellular components

Question 13

Which of the following is a correct pairing of an antimicrobial food preservative and its specific application?

Accepted Answer

Sorbic acid is used to inhibit molds in cheeses and baked goods.

Question 14

Which of the following is a distinguishing feature between iodine tinctures/iodophors and bleach/chlorine as disinfectants?

Accepted Answer

Iodine compounds are less corrosive and more stable in organic matter than chlorine compounds.

Question 15

A laboratory is using filtration to sterilize a heat-sensitive antibiotic solution. Which pore size filter should be used to effectively remove bacteria?

Accepted Answer

$$0.22\ \mu m$$

Question 16

Which of the following is NOT a standard condition for steam autoclaving?

Accepted Answer

$$63^\circ C$$ for 30 minutes

Question 17

Which of the following best describes the action of phenolic compounds as disinfectants?

Accepted Answer

They disrupt plasma membranes and denature proteins.

Question 18

Which of the following is a limitation of using dry heat sterilization (e.g., hot air oven)?

Accepted Answer

It requires higher temperatures and longer exposure times compared to moist heat sterilization.

Question 19

Which of the following is a correct statement about the use of aldehydes as chemical sterilants?

Accepted Answer

Aldehydes inactivate proteins and nucleic acids by cross-linking functional groups.

Question 20

A patient develops a hospital-acquired infection after surgery. Which of the following best describes this type of infection?

Accepted Answer

Nosocomial infection

Microbial Control: Sterilization, Disinfection, and Antimicrobial Methods

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