A carbapenem-resistant Klebsiella pneumoniae isolate produces an enzyme that is not inhibited by EDTA (a chelator of Zn2+) but is inhibited by clavulanic acid-based inhibitors. This resistance phenotype is most consistent with:
- A NDM (New Delhi Metallo-beta-lactamase) — a Class B metallo-beta-lactamase inhibited by EDTA
- B OXA-48 — a Class D oxacillinase partially inhibited by clavulanic acid and resistant to EDTA
- C VIM (Verona Integron-encoded Metallo-beta-lactamase) — Class B, EDTA-sensitive
- D KPC (Klebsiella pneumoniae carbapenemase) — a Class A serine carbapenemase inhibited by boronic acid compounds ✓
Explanation
KPC (Klebsiella pneumoniae carbapenemase) is a Ambler Class A serine carbapenemase encoded by blaKPC on a Tn4401 transposon typically on plasmids. Unlike metallo-beta-lactamases (Class B: NDM, VIM, IMP), KPC does not require zinc as a cofactor and is therefore NOT inhibited by EDTA. KPC is partially inhibited by older beta-lactam inhibitors including clavulanic acid and tazobactam (though at higher concentrations); newer inhibitors like avibactam, relebactam, and vaborbactam effectively inhibit KPC. NDM and VIM are Class B metallo-beta-lactamases that require Zn2+ and are inhibited by EDTA. OXA-48 (Class D) is not inhibited by clavulanic acid and not inhibited by EDTA.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.