OXA-48-type carbapenemases in Klebsiella pneumoniae are clinically important because they:
- A Hydrolyze carbapenems via metallo-beta-lactamase activity requiring zinc cofactors
- B Are class D serine oxacillinases that hydrolyze carbapenems weakly but are poorly inhibited by clavulanate or tazobactam, and are often missed by phenotypic tests ✓
- C Confer resistance to ceftazidime-avibactam because avibactam cannot inhibit metallo-enzymes
- D Are plasmid-mediated class A enzymes hydrolyzed by avibactam combinations
Correct answer: B. Are class D serine oxacillinases that hydrolyze carbapenems weakly but are poorly inhibited by clavulanate or tazobactam, and are often missed by phenotypic tests
Explanation
OXA-48 and variants (OXA-181, OXA-232) are class D serine beta-lactamases (not metallo-enzymes — option A describes NDM/VIM/IMP). They hydrolyze carbapenems weakly but are resistant to traditional inhibitors (clavulanate, sulbactam, tazobactam). Importantly, OXA-48 hydrolytic activity is low enough to be missed by routine phenotypic carbapenem MIC testing, posing a detection challenge. Crucially, avibactam DOES inhibit OXA-48 (unlike NDM), so ceftazidime-avibactam is active against OXA-48 producers but NOT against NDM/VIM producers.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.