Question 1

Which scientist is credited with the discovery of penicillin, and what was the source organism?

Accepted Answer

Alexander Fleming; Penicillium

Question 2

What is the primary reason why antibiotics that inhibit cell wall synthesis, such as penicillin, do not harm mammalian cells?

Accepted Answer

Mammalian cells lack peptidoglycan in their cell walls.

Question 3

Which genus of bacteria is responsible for producing more than half of all known antibiotics?

Accepted Answer

Streptomyces

Question 4

A patient develops a secondary infection with antibiotic-resistant bacteria after broad-spectrum antibiotic therapy. What is this phenomenon called?

Accepted Answer

Superinfection

Question 5

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

Accepted Answer

Competitive inhibition of folic acid synthesis

Question 6

Why are viral infections more difficult to treat with chemotherapy than bacterial infections?

Accepted Answer

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

Question 7

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

Accepted Answer

Isoniazid

Question 8

Aminoglycosides, such as streptomycin, inhibit bacterial growth by:

Accepted Answer

Changing the shape of the 30S ribosomal subunit, causing mRNA misreading

Question 9

Which of the following best explains why sulfa drugs selectively harm bacteria but not human cells?

Accepted Answer

Humans obtain folic acid from their diet, while bacteria must synthesize it.

Question 10

Which of the following is a common mechanism by which bacteria develop resistance to penicillin?

Accepted Answer

Production of beta-lactamase enzymes

Question 11

A patient is prescribed both penicillin and tetracycline. What is a possible outcome of this drug combination?

Accepted Answer

Antagonism, as tetracycline inhibits bacterial growth needed for penicillin action

Question 12

Which of the following drugs is used topically and is effective against gram-negative bacteria by disrupting the plasma membrane?

Accepted Answer

Polymyxin B

Question 13

Which of the following statements about broad-spectrum antibiotics is correct?

Accepted Answer

They can lead to superinfections by disrupting normal microbiota.

Question 14

Which of the following is a correct description of the Kirby-Bauer disk diffusion test?

Accepted Answer

It determines the sensitivity of bacteria to antibiotics by measuring the zone of inhibition.

Question 15

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

Accepted Answer

Inhibition of DNA gyrase, preventing DNA replication

Question 16

A new antibiotic is found to bind to the 50S/30S interface of the bacterial ribosome. Which class does it most likely belong to?

Accepted Answer

Oxazolidinones

Question 17

Which of the following is a real-world example of drug synergism?

Accepted Answer

Combining trimethoprim and sulfamethoxazole for urinary tract infections

Question 18

Which of the following is a target of antifungal drugs such as amphotericin B and azoles?

Accepted Answer

Ergosterol in the fungal plasma membrane

Question 19

Which of the following best explains why acyclovir is effective against viral infections but not toxic to human cells?

Accepted Answer

It only inhibits viral DNA polymerase, which is structurally different from human DNA polymerase.

Question 20

Which of the following mechanisms is NOT a common way bacteria develop resistance to antibiotics?

Accepted Answer

Increased synthesis of peptidoglycan

Antimicrobial Drugs: Mechanisms, Classes, and Resistance

Study Guide - Practice Questions