Question 1

Which of the following best describes the primary mode of action of ethylene oxide as a chemical sterilant?

Accepted Answer

It alkylates functional groups in proteins and nucleic acids, resulting in cross-linking and inactivation.

Question 2

A hospital needs to sterilize arthroscopic surgical instruments with small diameter tubes. Which method is most appropriate and why?

Accepted Answer

Plasma sterilization, because radicals formed in plasma can penetrate and destroy endospore-forming bacteria in complex instruments.

Question 3

Which of the following mechanisms allows bacteria to resist the effects of beta-lactam antibiotics such as penicillin?

Accepted Answer

Production of beta-lactamase enzymes that hydrolyze the beta-lactam ring.

Question 4

A water treatment facility is considering options for disinfecting water contaminated with anthrax endospores. Which chemical is most suitable and why?

Accepted Answer

Chlorine dioxide, because it is stable in water and effective against anthrax endospores.

Question 5

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

Accepted Answer

It requires several hours of exposure and is flammable and toxic.

Question 6

Peracetic acid is used to disinfect fruits and vegetables. Which property makes it particularly suitable for this application?

Accepted Answer

It leaves no toxic residues after disinfection.

Question 7

Which of the following best explains how plasma sterilization achieves microbial control?

Accepted Answer

Radicals formed in plasma destroy proteins and nucleic acids, including those of endospore-forming bacteria.

Question 8

A bacterial strain is found to rapidly expel antibiotics from its cells, rendering treatment ineffective. Which resistance mechanism is this?

Accepted Answer

Rapid efflux via efflux pumps.

Question 9

Which of the following is NOT a mechanism by which antimicrobial drugs act?

Accepted Answer

Promotion of membrane permeability.

Question 10

Supercritical carbon dioxide is used as a disinfectant. Which property allows it to destroy vegetative organisms and endospores at only $$45\ ^\circ \mathrm{C}$$?

Accepted Answer

It has increased solubility and lowered surface tension, allowing penetration and effectiveness at low temperatures.

Question 11

A patient is infected with a bacterium that has a mutated penicillin-binding protein. Which resistance mechanism is this an example of?

Accepted Answer

Alteration of drug target site.

Question 12

Which of the following best describes the effect of damaging nucleic acids in microbial cells?

Accepted Answer

Cells cannot synthesize essential proteins or replicate, leading to growth inhibition.

Question 13

Which antimicrobial drug mechanism would be most effective against a bacterium with a thick peptidoglycan cell wall?

Accepted Answer

Inhibition of cell wall synthesis.

Question 14

A new disinfectant is being tested for its ability to kill endospores within 30 minutes and bacteria/fungi within 5 minutes, leaving no toxic residues. Which chemical fits this description?

Accepted Answer

Peracetic acid.

Question 15

Which of the following is a plausible reason why a bacterium might prevent the penetration of an antibiotic to its target site?

Accepted Answer

Modified membrane proteins block the influx of antibiotics.

Question 16

A food processing plant needs a sterilant that is FDA approved, leaves no toxic residues, and is effective against viruses, bacteria, fungi, and endospores. Which should they use?

Accepted Answer

Peracetic acid.

Question 17

Which of the following is a real-world application of chlorine dioxide?

Accepted Answer

Fumigation of buildings contaminated with anthrax endospores.

Question 18

A bacterium expresses efflux pumps that are normally used to eliminate toxic substances. Which antibiotic resistance mechanism does this illustrate?

Accepted Answer

Rapid efflux.

Question 19

Which of the following actions of microbial control agents would most likely cause cellular contents to leak out, interfering with growth?

Accepted Answer

Alteration of membrane permeability.

Question 20

A scientist is designing a sterilization protocol for heat-sensitive medical equipment. Which method would be most effective and why?

Accepted Answer

Ethylene oxide, because it sterilizes even endospores at ambient temperature and is highly penetrating.

Microbial Control and Antimicrobial Drugs: Mechanisms and Resistance

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