Macrolides exert their antibacterial effect primarily by which mechanism?

Explanation

## Mechanism of Action of Macrolides **Key Point:** Macrolides are macrocyclic lactone antibiotics that bind irreversibly to the bacterial 50S ribosomal subunit, inhibiting peptide bond formation and causing premature chain termination. ### Binding Site and Effect Macrolides bind to the 23S rRNA component of the 50S ribosomal subunit in bacteria. This binding: - Prevents translocation of peptides - Inhibits protein synthesis - Results in bacteriostatic activity (not bactericidal) ### Why Other Options Are Wrong | Mechanism | Antibiotic Class | Example | |-----------|------------------|----------| | DNA gyrase inhibition | Fluoroquinolones | Ciprofloxacin | | Cell wall synthesis | Beta-lactams | Penicillin, Cephalosporin | | Folate metabolism | Sulfonamides, Trimethoprim | Sulfamethoxazole | **High-Yield:** The 50S ribosomal subunit is the hallmark target of macrolides, linezolid, and chloramphenicol — remember this triad for NEET PG. **Clinical Pearl:** Macrolides are bacteriostatic, meaning they stop bacterial growth but rely on the immune system for clearance. This is why they are less effective in immunocompromised patients.