A patient in the ICU develops fever on day 8 of mechanical ventilation. BAL is performed and quantitative culture grows ≥10^4 CFU/mL of Acinetobacter baumannii. The isolate is resistant to imipenem, meropenem, and colistin. What combination is used for carbapenem-resistant Acinetobacter baumannii (CRAB) with colistin resistance?
- A Cefiderocol ± sulbactam-durlobactam or high-dose ampicillin-sulbactam with polymyxin B ✓
- B Tigecycline monotherapy at standard doses
- C Azithromycin + rifampicin synergy regimen
- D Vancomycin + meropenem as MIC creep is overestimated
Explanation
CRAB (carbapenem-resistant Acinetobacter baumannii) is a WHO critical priority pathogen. When colistin resistance is also present (pan-drug resistant, PDR), therapeutic options are severely limited. Cefiderocol (a novel siderophore cephalosporin that uses iron transporters to enter cells, bypassing outer membrane impermeability) has activity against CRAB. Sulbactam has intrinsic activity against A. baumannii (inhibits PBP1 and PBP3) and the novel beta-lactamase inhibitor durlobactam restores sulbactam activity against beta-lactamase-producing CRAB. High-dose ampicillin-sulbactam is another option. Tigecycline monotherapy gives poor bacteraemia outcomes due to low serum levels.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
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