Question 1

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

Accepted Answer

Sterilization removes all forms of microbial life, including endospores, while disinfection reduces the number of pathogens but may not eliminate all microbes or endospores.

Question 2

A surgeon uses aseptic techniques during surgery. Which of the following best defines 'asepsis'?

Accepted Answer

The absence of pathogenic microorganisms from living tissue.

Question 3

Which suffix indicates an agent that kills microbes, and which indicates an agent that inhibits their growth?

Accepted Answer

‘-cide’ means to kill; ‘-static’ means to inhibit growth.

Question 4

Which of the following factors does NOT influence the rate of microbial death when using a chemical disinfectant?

Accepted Answer

The color of the disinfectant.

Question 5

A hospital needs to sterilize heat-sensitive surgical instruments. Which method is most appropriate?

Accepted Answer

Ethylene oxide gas sterilization.

Question 6

Which equation best represents the decimal reduction time ($$D) in $$microbial control?

Accepted Answer

The time required to reduce the microbial population by 90% at a given temperature: $$D = 	ext{time for 1 log reduction}$$

Question 7

Which of the following statements about autoclaves is correct?

Accepted Answer

Autoclaves use moist heat under pressure to achieve sterilization, typically at $$121\ ^\circ \mathrm{C}$$ and 15 psi for 15 minutes.

Question 8

Which physical method of microbial control is most effective for removing bacteria from heat-sensitive liquids, such as vaccines?

Accepted Answer

Filtration using membrane filters.

Question 9

HEPA filters are used in hospital isolation rooms. What does HEPA stand for and what is its primary function?

Accepted Answer

High-Efficiency Particulate Air; removes airborne microbes and particles.

Question 10

Which of the following best describes the mechanism of action for ionizing radiation in microbial control?

Accepted Answer

Ionizing radiation causes the formation of free radicals that damage DNA, leading to microbial death.

Question 11

A food processing plant uses ultraviolet (UV) light to disinfect surfaces. Which statement best describes the mechanism of non-ionizing radiation?

Accepted Answer

UV light causes thymine dimers in DNA, inhibiting replication and leading to cell death.

Question 12

Which of the following is a challenge when using microwaves to control microbial growth?

Accepted Answer

Microwaves may not evenly heat materials, leading to survival of some microbes.

Question 13

Which chemical control method is most appropriate for disinfecting drinking water in a municipal supply?

Accepted Answer

Chlorine-based compounds such as bleach or chloramine.

Question 14

Which equation best represents the effectiveness of alcohol as a disinfectant?

Accepted Answer

Alcohol is most effective at concentrations of $$60\% to$$ $$95\%$$, as water is required for protein denaturation.

Question 15

Which of the following best explains the principle of oligodynamic action in heavy metal chemical controls?

Accepted Answer

Small amounts of heavy metals exert antimicrobial effects by denaturing proteins.

Question 16

Why are organic acids commonly used as food preservatives?

Accepted Answer

They inhibit microbial growth by lowering pH and interfering with metabolism.

Question 17

Which of the following best describes the mechanism of action for aldehydes in microbial control?

Accepted Answer

Aldehydes cross-link proteins and nucleic acids, leading to microbial death.

Question 18

A laboratory technician uses the disk diffusion method to evaluate the effectiveness of a new disinfectant. Which statement best describes this method?

Accepted Answer

A chemical-impregnated disk is placed on an agar plate inoculated with bacteria; the zone of inhibition is measured to assess effectiveness.

Question 19

Which form of toxic oxygen is most commonly used to disinfect medical equipment, and what is its mechanism?

Accepted Answer

Hydrogen peroxide ($$\mathrm{H}_2\mathrm{O}_2$$); produces free radicals that damage cellular components.

Control of Microbial Growth: Principles and Methods

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