Aminoglycosides require active transport across the bacterial inner membrane for entry. This transport is oxygen-dependent, explaining why aminoglycosides are ineffective against:

• A Strictly anaerobic bacteria (lack electron transport chain needed for active uptake) ✓
• B Gram-positive cocci (lack outer membrane)
• C Mycobacteria (aminoglycosides cannot penetrate the mycobacterial cell wall)
• D Intracellular organisms (cannot enter eukaryotic cells)

Explanation

Aminoglycosides enter bacteria via an energy-dependent active transport system (EDP-I, EDP-II) that is driven by the electron transport chain proton-motive force; strictly anaerobic bacteria lack a functional aerobic respiratory chain and therefore cannot generate the required electrochemical gradient for aminoglycoside uptake. This explains the complete lack of aminoglycoside activity against anaerobes. Aminoglycosides do enter mycobacteria (streptomycin and amikacin are used for TB), and they do not require uptake into eukaryotic cells for bacterial killing.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.