Beta-lactamase inhibitors such as avibactam differ fundamentally from clavulanate in their mechanism. Which property best describes this difference?

• A Avibactam inhibits beta-lactamase by binding to the active site zinc ions, unlike clavulanate which inhibits serine enzymes
• B Avibactam is a non-beta-lactam that forms a covalent but reversible acyl-enzyme complex, enabling recycling to inhibit more enzyme ✓
• C Avibactam is a beta-lactam ring compound that undergoes progressive suicide inhibition like sulbactam
• D Avibactam blocks OmpF porins preventing beta-lactamase secretion into the periplasmic space

Explanation

Avibactam is a diazabicyclooctane (DBO) non-beta-lactam beta-lactamase inhibitor. It covalently acylates the active site serine of class A, class C, and some class D beta-lactamases, but — unlike clavulanate which undergoes irreversible progressive suicide inactivation — the acyl-enzyme complex can regenerate (deacylate), releasing free avibactam capable of inhibiting additional enzyme molecules. This recycling mechanism gives avibactam superior activity against high-level enzyme producers. Importantly, avibactam does not inhibit metallo-beta-lactamases (class B, e.g., NDM-1), which require zinc at the active site; those require aztreonam combination or cefiderocol.

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

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