Aminoglycosides such as gentamicin are bactericidal against aerobic Gram-negative bacilli. Their primary mechanism of action is:

• A Inhibiting the 50S subunit translocation step
• B Blocking peptidyl transferase at the 50S subunit
• C Preventing attachment of aminoacyl-tRNA to the acceptor site
• D Binding to the 30S ribosomal subunit and causing misreading of mRNA codons ✓

Explanation

Aminoglycosides bind irreversibly to the 30S subunit, specifically near the D site, which interferes with the initiation complex and causes misreading of codons, leading to incorporation of wrong amino acids and nonfunctional proteins. This misreading accounts for their bactericidal action, unusual among protein synthesis inhibitors. Option B describes chloramphenicol, option C describes tetracyclines, and option A describes macrolides.

Reference: Katzung Basic and Clinical Pharmacology, 15th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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