Treatment of Carbapenem-Resistant Acinetobacter baumannii Infections
Introduction to Treatment Guidelines
- The Infectious Diseases Society of America recommends using colistin with a loading dose of 5 mg CBA/kg IV followed by 2.5 mg CBA × (1.5 × CrCl + 30) IV every 12 hours, combined with either high-dose carbapenem or high-dose sulbactam plus tigecycline for the treatment of carbapenem-resistant A. baumannii infections 1
Treatment Algorithm by Infection Site
- For CRAB pneumonia, administer IV colistin with a loading dose of 5 mg CBA/kg, then maintenance of 2.5 mg CBA × (1.5 × CrCl + 30) every 12 hours, and add high-dose carbapenem if carbapenem MIC ≤32 mg/L 1
- For CRAB bloodstream infections, use IV colistin with the same dosing as pneumonia, and add high-dose carbapenem if MIC ≤32 mg/L 1
- For CRAB urinary tract infections, use ampicillin-sulbactam 3g sulbactam every 8 hours as 4-hour infusion for sulbactam-susceptible isolates, or colistin with loading dose 6-9 million IU, then 9 million IU/day in 2-3 divided doses for sulbactam-resistant isolates 2
Treatment Selection Based on Susceptibility Testing
- If carbapenem-susceptible A. baumannii, use carbapenems as first-line in areas with low carbapenem resistance, but avoid using ertapenem due to its lack of activity against A. baumannii 3
- If sulbactam-susceptible, ampicillin-sulbactam is preferred over polymyxins due to a better safety profile, with a dose of 3g sulbactam every 8 hours as 4-hour infusion 2
Combination Therapy Considerations
- The American Thoracic Society recommends combination therapy with two active agents, such as colistin + carbapenem or colistin + sulbactam + tigecycline, for severe CRAB infections, especially septic shock 1
- Avoid combining colistin with rifampin, vancomycin, or other glycopeptides due to increased nephrotoxicity without benefit 3