Question 1

Which of the following best describes selective toxicity in antimicrobial drugs?

Accepted Answer

The ability to kill harmful microbes without damaging the host

Question 2

Which of the following drugs is most effective against Mycobacterium tuberculosis due to its inhibition of mycolic acid synthesis?

Accepted Answer

Isoniazid

Question 3

A patient is prescribed a drug that binds to the 50S ribosomal subunit and inhibits peptide bond formation. Which drug is this most likely to be?

Accepted Answer

Chloramphenicol

Question 4

Which of the following is a reason why penicillin is generally ineffective against most gram-negative bacteria?

Accepted Answer

Penicillin cannot pass through the outer membrane porin channels of gram-negative bacteria

Question 5

Which of the following best explains why sulfa drugs (sulfonamides) are selectively toxic to bacteria but not to humans?

Accepted Answer

Sulfa drugs interfere with folic acid synthesis, which bacteria must perform but humans obtain from their diet

Question 6

A patient with a fungal infection is treated with amphotericin B. What is the primary mechanism of action of this drug?

Accepted Answer

Disruption of plasma membrane by binding to ergosterol

Question 7

Which of the following is a common mechanism by which bacteria develop resistance to beta-lactam antibiotics such as penicillin?

Accepted Answer

Production of beta-lactamase (penicillinase) enzymes

Question 8

A physician wants to determine the minimum inhibitory concentration (MIC) of an antibiotic for a bacterial isolate. Which laboratory method should be used?

Accepted Answer

Broth dilution test

Question 9

Which of the following combinations of drugs is likely to be antagonistic when used together?

Accepted Answer

Penicillin and tetracycline

Question 10

Which of the following statements about the Kirby-Bauer disk diffusion test is TRUE?

Accepted Answer

The size of the zone of inhibition is directly proportional to the effectiveness of the antibiotic

Question 11

Which of the following antibiotics is produced by Streptomyces griseus and is effective against Mycobacterium tuberculosis?

Accepted Answer

Streptomycin

Question 12

A patient is prescribed a drug that inhibits DNA gyrase, leading to inhibition of DNA replication. Which drug is this most likely to be?

Accepted Answer

Ciprofloxacin

Question 13

Which of the following is a potential side effect of tetracycline use, especially in children?

Accepted Answer

Discoloration of teeth

Question 14

Which of the following best describes the action of macrolide antibiotics such as erythromycin?

Accepted Answer

Bind to the 50S ribosomal subunit and prevent translocation

Question 15

Which of the following is a reason why antiviral drugs are generally more difficult to develop than antibacterial drugs?

Accepted Answer

Viruses use host cell machinery for replication, making selective toxicity difficult

Question 16

A patient with a tapeworm infection is treated with a drug that prevents ATP generation in the parasite. Which drug is this most likely to be?

Accepted Answer

Niclosamide

Question 17

Which of the following is a common misuse of antibiotics that can lead to increased resistance?

Accepted Answer

Using antibiotics for viral infections like the common cold

Question 18

Which of the following best explains why penicillin is considered to have selective toxicity?

Accepted Answer

It inhibits peptidoglycan synthesis, which is unique to bacterial cell walls

Question 19

Which of the following is the main reason why combination therapy with two antibiotics may be synergistic?

Accepted Answer

The combined effect is greater than the sum of the effects of each drug alone

Question 20

Which of the following statements about the E test is TRUE?

Accepted Answer

It provides a direct measurement of the minimum inhibitory concentration (MIC)

Antimicrobial Drugs: Mechanisms, Classes, and Clinical Applications

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