Question 1

Which of the following best describes the process of sterilization?

Accepted Answer

The destruction of all forms of microbial life, including endospores.

Question 2

A hospital is preparing surgical instruments for use. Which method would ensure sterilization, including the destruction of endospores, in the shortest time?

Accepted Answer

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

Question 3

Which of the following statements about microbial death is correct?

Accepted Answer

Microbial death occurs at a constant rate when plotted on a logarithmic scale.

Question 4

A laboratory technician needs to sterilize a heat-sensitive solution. Which method is most appropriate?

Accepted Answer

Filtration through a membrane with pores of $$0.22\ \mu m.$$

Question 5

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

Accepted Answer

Moist heat transfers heat more rapidly due to water's higher heat capacity.

Question 6

A food manufacturer wants to prevent the growth of Clostridium botulinum in canned meats. Which chemical preservative should be used?

Accepted Answer

Sodium nitrate

Question 7

Which of the following is a limitation of using alcohols as disinfectants?

Accepted Answer

They do not kill endospores or nonenveloped viruses.

Question 8

A patient with a wound infected by an anaerobic pathogen is treated with benzoyl peroxide. What is the primary mechanism of action of this agent?

Accepted Answer

Oxidation of cellular components

Question 9

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

Accepted Answer

They are strongly bactericidal against gram-positive bacteria.

Question 10

A researcher is using UV light to sterilize surfaces in a laboratory. Which wavelength is most effective for killing microbes, and what is the primary target?

Accepted Answer

About $$260\ nm$$; damages DNA by forming thymine dimers.

Question 11

Which of the following best explains why gram-negative bacteria are generally more resistant to disinfectants than gram-positive bacteria?

Accepted Answer

They possess an outer membrane that restricts entry of chemicals.

Question 12

A nurse is preparing a patient's skin for surgery using an alcohol swab. Which term best describes this process?

Accepted Answer

Degerming

Question 13

Which of the following is a correct statement about the use of hydrogen peroxide as an antiseptic?

Accepted Answer

It is quickly broken down by catalase in tissues, reducing its effectiveness on open wounds.

Question 14

A microbiologist is testing a new disinfectant. Which factors should be considered to ensure effective disinfection?

Accepted Answer

Concentration, nature of the material, contact time, and temperature.

Question 15

Which of the following chemical agents is most appropriate for sterilizing heat-sensitive medical equipment in a closed chamber?

Accepted Answer

Ethylene oxide

Question 16

A scientist is using a HEPA filter to sterilize air in a laboratory. What is the minimum particle size that a HEPA filter can effectively remove?

Accepted Answer

$$0.3\ \mu m$$

Question 17

Which of the following best describes the action of aldehydes such as glutaraldehyde in microbial control?

Accepted Answer

They denature proteins by forming covalent cross-links with organic functional groups.

Question 18

A food product is preserved by adding high concentrations of salt. What is the primary mechanism by which this inhibits bacterial growth?

Accepted Answer

Salt causes plasmolysis by drawing water out of the cell.

Question 19

Which of the following is a correct statement about the use of phenolics in disinfection?

Accepted Answer

Phenolics remain active in the presence of organic matter and are good for cleaning up pus, saliva, and feces.

Question 20

A hospital is evaluating two disinfectants using a use-dilution test. Disinfectant A kills all test organisms in 5 minutes, while Disinfectant B requires 15 minutes. If both are used at the same concentration and temperature, which has the higher rate constant $$k$$ for microbial death, assuming first-order kinetics ($$N_t = N_0$ e$$^{-kt}$$)?

Accepted Answer

Disinfectant A, because a shorter time to kill indicates a higher $$k$$ value.

Control of Microbial Growth: Principles and Methods

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