Question 1

Which of the following best describes the mechanism of action of vancomycin?

Accepted Answer

It blocks the transport of N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) groups across the cytoplasmic membrane.

Question 2

A patient is prescribed a broad-spectrum antibiotic for a suspected bacterial infection. Which of the following is a significant risk associated with the use of broad-spectrum antibiotics?

Accepted Answer

They can disrupt normal microbiota, leading to secondary infections such as Clostridioides difficile.

Question 3

Which of the following antibiotics inhibits protein synthesis by blocking the proper movement of the ribosome along mRNA, causing 'ribosomal stalling'?

Accepted Answer

Erythromycin

Question 4

A bacterial strain develops resistance to penicillin by producing an enzyme that degrades the drug. What is the name of this enzyme?

Accepted Answer

Beta-lactamase

Question 5

Which of the following best explains why selective toxicity is harder to achieve with antiviral and antifungal drugs compared to antibacterial drugs?

Accepted Answer

Viruses use host cell machinery and fungi are eukaryotic, making it difficult to target them without harming host cells.

Question 6

A laboratory is testing the efficacy of a new antibiotic. They determine the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC). What is the difference between MIC and MBC?

Accepted Answer

MIC is the lowest concentration that inhibits visible growth; MBC is the lowest concentration that kills 99.9% of the bacteria.

Question 7

Which of the following is a mechanism by which bacteria can acquire antibiotic resistance?

Accepted Answer

By acquiring R plasmids through horizontal gene transfer.

Question 8

A patient is treated with streptomycin for tuberculosis. What is the primary mechanism by which streptomycin inhibits bacterial growth?

Accepted Answer

It causes distortion/bulging of the 30S ribosomal subunit, inhibiting protein synthesis.

Question 9

Which of the following best describes the action of sulfonamides?

Accepted Answer

They inhibit metabolic pathways by acting as competitive inhibitors of folic acid synthesis.

Question 10

A bacterial population is exposed to an antibiotic. Over time, the population becomes resistant. Which of the following best explains how this resistance develops?

Accepted Answer

The antibiotic selects for pre-existing resistant bacteria, which then proliferate.

Question 11

Which of the following antibiotics inhibits DNA topoisomerase/gyrase activity, thereby preventing DNA replication?

Accepted Answer

Ciprofloxacin

Question 12

A patient develops a secondary infection after antibiotic treatment. Which of the following best explains this phenomenon?

Accepted Answer

The antibiotic disrupted the normal microbiota, allowing opportunistic pathogens to proliferate.

Question 13

Which of the following is a plausible reason why treatment of diseases not directly related to infectious disease may be affected if we lose effective antibiotics?

Accepted Answer

Antibiotics are essential for preventing infections during surgeries and cancer treatments.

Question 14

Which of the following best describes the action of polymyxin?

Accepted Answer

It disrupts the cytoplasmic membrane, leading to cell lysis.

Question 15

A bacterial cell is found to be resistant to multiple antibiotics due to the presence of an R plasmid. Which of the following best describes an R plasmid?

Accepted Answer

A plasmid that carries genes for antibiotic resistance.

Question 16

Which of the following is a correct statement about the difference between bactericidal and bacteriostatic drugs?

Accepted Answer

Bactericidal drugs kill bacteria, while bacteriostatic drugs inhibit their growth.

Question 17

A new antibiotic is found to inhibit peptide bond formation during protein synthesis. Which of the following antibiotics shares this mechanism?

Accepted Answer

Chloramphenicol

Question 18

Which of the following is a major disadvantage of using the oral route for antibiotic administration?

Accepted Answer

It may be affected by stomach acid and first-pass metabolism, reducing drug efficacy.

Question 19

A bacterial isolate is found to be resistant to erythromycin due to an efflux pump. Which of the following best describes the function of an efflux pump in antibiotic resistance?

Accepted Answer

It pumps the antibiotic out of the cell, reducing intracellular concentration.

Question 20

Which of the following best explains why changing the structure of the antibiotic target can lead to resistance?

Accepted Answer

The antibiotic can no longer bind effectively to its target, rendering it ineffective.

Antimicrobial Drugs: Mechanisms, Efficacy, and Resistance

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