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Community-acquired pneumonia — USMLE Step 2 CK MCQ

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HardInternal MedicineCommunity-acquired pneumoniaUSMLE Step 2 CK

A 71-year-old man develops septic shock from a KPC-producing Klebsiella pneumoniae bloodstream infection. The isolate is susceptible to meropenem-vaborbactam, ceftazidime-avibactam and imipenem-cilastatin-relebactam but resistant to meropenem alone. He improves after initial empiric therapy. Which definitive regimen is preferred?

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Correct answer: D — Use meropenem-vaborbactam as targeted therapy

Meropenem-vaborbactam is an active preferred newer beta-lactam/beta-lactamase inhibitor for invasive KPC-producing CRE, and targeted monotherapy is sufficient once susceptibility is established. Extended-infusion meropenem cannot overcome documented meropenem resistance. Adding meropenem to ceftazidime-avibactam or colistin to meropenem provides no routine benefit and adds toxicity. Tigecycline has poor serum exposure for bacteremia, while gentamicin adds nephrotoxicity.

Reference: IDSA 2024 guidance on antimicrobial-resistant gram-negative infections: https://www.idsociety.org/practice-guideline/amr-guidance