A 24-year-old woman treated for uncomplicated urinary tract infection develops Achilles tendon pain after completing the antibiotic course. The drug she received inhibits which enzyme?
- A DNA-dependent RNA polymerase
- B DNA gyrase (bacterial topoisomerase II) ✓
- C Dihydrofolate reductase
- D Ribosomal 30S subunit
Correct answer: B. DNA gyrase (bacterial topoisomerase II)
Explanation
Fluoroquinolones such as ciprofloxacin inhibit bacterial DNA gyrase (topoisomerase II) and topoisomerase IV, enzymes that relieve supercoils and decatenate daughter chromosomes. Tendinopathy and tendon rupture are recognized adverse effects. Rifampin targets RNA polymerase, trimethoprim targets dihydrofolate reductase, and aminoglycosides and tetracyclines target the 30S subunit, so these distractors map onto other well-known drug classes rather than this presentation.
Reference: Katzung's Basic and Clinical Pharmacology, 16th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.