Aminoglycoside uptake into bacteria is energy-dependent and requires the electron transport chain. This explains why aminoglycosides are poorly effective against:
- A Strictly anaerobic bacteria such as Bacteroides fragilis ✓
- B Pseudomonas aeruginosa
- C Gram-positive cocci when used without a cell-wall-active agent
- D Mycobacterium tuberculosis
Correct answer: A. Strictly anaerobic bacteria such as Bacteroides fragilis
Explanation
Aminoglycoside transport across the bacterial inner membrane requires an electrochemical gradient maintained by the electron transport chain (ETC). Obligate anaerobes lack an aerobic ETC, so they cannot generate the membrane potential required for drug uptake; consequently, aminoglycosides have no clinically useful activity against anaerobes. This is also why aminoglycosides are combined with beta-lactams for synergistic killing of enterococci (permeabilisation by cell-wall damage enables aminoglycoside entry).
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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