Ethambutol is active against mycobacteria because it inhibits the synthesis of which cell wall component?
- A Mycolic acid
- B Peptidoglycan
- C Arabinogalactan ✓
- D Lipopolysaccharide
Correct answer: C. Arabinogalactan
Explanation
Ethambutol inhibits arabinosyltransferases (embAB gene products), blocking incorporation of arabinose into arabinogalactan, a key cell wall polysaccharide. This weakens the mycobacterial cell wall and enhances penetration of other drugs. Mycolic acid synthesis is inhibited by isoniazid and ethionamide. Resistance arises from embB mutations, particularly at codon 306.
Reference: Katzung Basic and Clinical Pharmacology, 15th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.