Which specific action of aminoglycosides accounts for their bactericidal activity against aerobic Gram-negative bacilli?
- A Binding to the 16S rRNA component of the 30S subunit, causing misreading of mRNA and blocking initiation complex formation ✓
- B Binding to the 50S subunit and inhibiting peptidyl transferase
- C Inhibiting the enzyme DNA gyrase and preventing supercoiling
- D Blocking the attachment of aminoacyl-tRNA to the ribosomal acceptor site
Correct answer: A. Binding to the 16S rRNA component of the 30S subunit, causing misreading of mRNA and blocking initiation complex formation
Explanation
Aminoglycosides bind irreversibly to the 16S rRNA of the 30S subunit at the B site. This produces two effects: misreading of the codon message so wrong amino acids enter the growing peptide, and inhibition of initiation complex formation. Option D describes tetracyclines, option B describes chloramphenicol, and option C describes fluoroquinolones. Their oxygen-dependent uptake also explains activity limited to aerobes.
Reference: Katzung Basic and Clinical Pharmacology, 16th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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