Fosfomycin exerts its antibacterial effect by inhibiting which step in bacterial cell wall peptidoglycan synthesis?

• A Transpeptidation of pentapeptide cross-links (PBP inhibition)
• B Bactoprenol-mediated lipid II translocation across the membrane
• C D-Ala-D-Ala ligase involved in pentapeptide precursor synthesis
• D MurA enzyme — the first committed step forming UDP-N-acetylmuramic acid ✓

Explanation

Fosfomycin is a phosphonic acid antibiotic that covalently and irreversibly inhibits MurA (UDP-N-acetylglucosamine enolpyruvyl transferase), the enzyme catalysing the first committed step in peptidoglycan biosynthesis — the addition of phosphoenolpyruvate to UDP-GlcNAc to form UDP-MurNAc. This unique mechanism means there is no cross-resistance with beta-lactams, glycopeptides, or other antibiotics. It is used orally for uncomplicated UTI caused by E. coli.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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