Aminoglycosides are inactive against anaerobic bacteria despite having activity against many facultative organisms. The primary reason for this lack of activity against anaerobes is:

• A Anaerobic organisms lack the 30S ribosomal subunit target of aminoglycosides
• B Anaerobic organisms constitutively express aminoglycoside-modifying enzymes
• C Aminoglycoside transport into bacterial cells requires an oxygen-dependent electron transport chain ✓
• D Aminoglycosides are rapidly degraded by anaerobic bacterial nitroreductases

Explanation

Aminoglycoside uptake requires energy-dependent transport driven by the electron transport chain, which is absent in obligate anaerobes. This explains their lack of anaerobic activity. Option A is incorrect because all bacteria possess the 30S ribosomal target. Option B describes a resistance mechanism, not an intrinsic spectrum limitation.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.