Treatment of Carbapenem-Resistant Acinetobacter baumannii (CRAB) Infections

First-Line Treatment Options

The Infectious Diseases Society of America recommends combination therapy over monotherapy for CRAB infections requiring polymyxin treatment, based on moderate-quality evidence showing reduced treatment failure rates and improved pathogen eradication 1, 2
For CRAB susceptible to sulbactam, the American Thoracic Society recommends ampicillin-sulbactam as the preferred treatment, particularly for hospital-acquired/ventilator-associated pneumonia (HAP/VAP) 3
For CRAB bloodstream infections (BSI), the Society for Healthcare Epidemiology of America recommends colistin-carbapenem based combination therapy, though this is a weak recommendation based on low-quality evidence 4, 5

The European Society of Clinical Microbiology and Infectious Diseases suggests colistin-carbapenem combinations for CRAB infections if meropenem MIC is ≤32 mg/L, using extended-infusion of meropenem for 3 hours 1, 2
For CRAB pneumonia, the International Society for Antimicrobial Chemotherapy recommends colistin-carbapenem combinations, which ranked highest for clinical cure (SUCRA 91.7%) and second for microbiological cure (SUCRA 68.7%) in network meta-analyses 6
Colistin-tigecycline combinations have shown the lowest mortality rates (SUCRA 93.4%) in some analyses 5

The American College of Chest Physicians strongly recommends against polymyxin-meropenem combination therapy for CRAB infections with high-level carbapenem resistance (MICs >16 mg/L) based on high-quality evidence from randomized controlled trials 7
The Infectious Diseases Society of America strongly recommends against polymyxin-rifampin combination therapy based on moderate quality evidence 7

The American Society of Health-System Pharmacists recommends careful attention to unit conversion for colistin dosing: 1 million U = 80 mg mass CMS = 33 mg colistin base activity (CBA) 1, 6
For sulbactam, the Society of Infectious Diseases Pharmacists recommends doses of 6-9g per day, typically administered as fixed-dose combinations (e.g., cefoperazone 1.5g/sulbactam 1.5g every 6h or ampicillin 18g/sulbactam 9g per day) 5

The American Thoracic Society suggests aerosolized polymyxin in addition to intravenous polymyxin for CRAB respiratory tract infections, though this is a weak recommendation based on low-quality evidence 6
Colistin methanesulfonate (CMS) is preferred for inhalation therapy 6

The National Kidney Foundation recommends monitoring renal function during polymyxin treatment, with therapeutic drug monitoring (TDM) encouraged when possible 1, 2
The American Society of Nephrology recommends avoiding ototoxic and nephrotoxic drugs in combination with polymyxin 1, 2
Nephrotoxicity is a significant concern with colistin therapy, occurring in up to 33% of patients 3

The European Society of Clinical Microbiology and Infectious Diseases recommends using tigecycline with caution, as monotherapy is not recommended for CRAB pneumonia due to higher treatment failure rates 5
For pan-resistant CRAB, treatment with antibiotics having the lowest MICs relative to breakpoints is recommended 3

The Infectious Diseases Society of America recommends that in vitro synergy testing may help guide therapy but does not always translate to clinical benefit 4
Colistin combination therapy appears to reduce treatment failure rates by approximately 119 cases per 1000 patients compared to monotherapy 1, 6