Question 1

Which of the following best describes the mechanism of action for penicillins?

Accepted Answer

They inhibit the synthesis of peptidoglycan, weakening the bacterial cell wall.

Question 2

A patient is prescribed a combination of amoxicillin and clavulanic acid (Augmentin). What is the primary purpose of adding clavulanic acid?

Accepted Answer

To inhibit β-lactamase enzymes that would otherwise degrade amoxicillin.

Question 3

Which equation correctly defines the therapeutic index (TI) of a drug?

Accepted Answer

$$TI = \frac{TD_{50}}{ED_{50}}$$

Question 4

Which of the following is a major reason why vancomycin is considered a last-resort antibiotic?

Accepted Answer

It is reserved for treating infections caused by MRSA and resistant gram-positive bacteria.

Question 5

Aminoglycosides, such as streptomycin, are unique among protein synthesis inhibitors because they:

Accepted Answer

Are bactericidal and cause mRNA misreading by altering the 30S ribosomal subunit.

Question 6

Which of the following best explains why sulfonamides selectively target bacteria but not human cells?

Accepted Answer

Bacteria synthesize their own folic acid, while humans obtain it from their diet.

Question 7

Which of the following is a common mechanism by which bacteria develop resistance to β-lactam antibiotics?

Accepted Answer

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

Question 8

A patient develops a superinfection after taking a broad-spectrum antibiotic. What is the most likely explanation?

Accepted Answer

The antibiotic suppressed normal microbiota, allowing opportunistic pathogens to proliferate.

Question 9

Which of the following statements about antifungal drugs is correct?

Accepted Answer

Polyenes bind ergosterol in fungal membranes, forming pores that disrupt membrane integrity.

Question 10

Which of the following best describes the action of quinolones such as ciprofloxacin?

Accepted Answer

They inhibit DNA gyrase, blocking bacterial DNA replication.

Question 11

A patient with a urinary tract infection is prescribed TMP-SMZ (Bactrim). Why is this combination more effective than either drug alone?

Accepted Answer

It blocks two sequential steps in folic acid synthesis, resulting in synergism.

Question 12

Which of the following is NOT a recommended strategy to prevent the development of antibiotic resistance?

Accepted Answer

Using antibiotics for viral infections such as the common cold.

Question 13

Which of the following best explains why combination therapy is used in the treatment of HIV?

Accepted Answer

It reduces the likelihood of resistance by targeting multiple steps in the viral life cycle.

Question 14

Which of the following drugs is used to treat malaria and acts by blocking the parasite's detoxification of heme?

Accepted Answer

Chloroquine

Question 15

A new antibiotic has a $$TD_{50} of 200 mg/kg $$and an $$ED_{50} of 10 mg/kg. $$What is its therapeutic index?

Accepted Answer

$$TI = \frac{200}{10} = 20$$

Question 16

Which of the following is a mechanism by which bacteria can prevent antibiotics from reaching their target site?

Accepted Answer

Modification of outer-membrane porins to block antibiotic entry.

Question 17

Which of the following statements about antiviral drugs is correct?

Accepted Answer

Nucleoside analogs inhibit viral RNA or DNA synthesis by mimicking natural nucleotides.

Question 18

Which of the following best describes the action of polymyxin B?

Accepted Answer

It binds to LPS in the gram-negative outer membrane, disrupting membrane integrity.

Question 19

Which of the following is a potential side effect of chloramphenicol that limits its use to serious infections?

Accepted Answer

Aplastic anemia due to suppression of bone marrow.

Question 20

Which of the following is a future strategy for antimicrobial therapy that aims to reduce the development of resistance?

Accepted Answer

Targeting virulence factors to disarm pathogens rather than kill them.

Antimicrobial Drugs: Mechanisms, Classes, and Resistance

Study Guide - Practice Questions