Which statement best describes the interaction between clavulanic acid and AmpC beta-lactamase?

• A. AmpC is not reliably inhibited by clavulanic acid, which affects interpretation
• B. AmpC is effectively inhibited by clavulanic acid
• C. Clavulanic acid induces AmpC expression
• D. AmpC production is not influenced by clavulanic acid

Answer: (A)

The key idea is that clavulanic acid does not reliably inhibit AmpC beta-lactamase. Clavulanic acid works well against many class A beta-lactamases, but AmpC enzymes (class C) have structural features that make them poor targets for this inhibitor. Because AmpC isn’t effectively blocked, using a beta-lactam combined with clavulanate won’t reliably restore antibiotic activity against AmpC producers. Clinically, this means susceptibility tests or interpretations that assume clavulanate will suppress AmpC can be misleading.

That’s why the statement describing AmpC as not reliably inhibited by clavulanic acid is the best choice. The other options imply that clavulanic acid either strongly inhibits AmpC, induces AmpC, or has no influence on AmpC production, which isn’t supported by how AmpC responds to clavulanate.