Question

Quinolones act on/interfere the :

• A. Bacterial cell wall synthesis
• B. Bacterial nucleic acid synthesis
• C. Viral nucleic acid synthesis
• D. Protein synthesis in bacteria

Hint:

Antibiotic mechanisms: Cell Wall (Penicillins, Cephalosporins), Protein Synthesis - 30S or 50S ribosomes (Tetracyclines, Macrolides), Nucleic Acid Synthesis (Quinolones, Rifampin).

Answer 1

The Correct Option is B

Step 1: Concept:
The question asks for the mechanism of action of a major class of antibiotics known as quinolones (and fluoroquinolones, like ciprofloxacin).

Step 2: Step-by-step Explanation:

• Quinolones are bactericidal antibiotics.

• They function by entering the bacterial cell and directly binding to and inhibiting two essential bacterial enzymes: DNA gyrase (topoisomerase II) and topoisomerase IV.

• DNA gyrase is responsible for unwinding the supercoiled DNA to allow the replication fork to proceed. By inhibiting this enzyme, quinolones physically halt DNA replication.

• Therefore, their primary mode of action is interfering with bacterial nucleic acid (DNA) synthesis.

• Contrast this with Penicillins (which inhibit cell wall synthesis) or Tetracyclines (which inhibit protein synthesis).

Step 3: Final Answer:
Quinolones interfere with bacterial nucleic acid synthesis, matching option (B).