Treatment of Acinetobacter Infections
For Acinetobacter infections, treatment should be based on antimicrobial susceptibility testing, with carbapenems as first-line therapy for susceptible isolates and polymyxins (colistin or polymyxin B) for carbapenem-resistant strains. 1, 2
Treatment Algorithm Based on Susceptibility
Carbapenem-Susceptible Acinetobacter
- Carbapenems (imipenem, meropenem, doripenem) are the drugs of choice for infections caused by susceptible A. baumannii in areas with low rates of carbapenem resistance 3, 2
- Recommended dosing:
Carbapenem-Resistant Acinetobacter
- For carbapenem-resistant A. baumannii that is sensitive only to polymyxins, intravenous polymyxin (colistin or polymyxin B) is strongly recommended 1, 2
- Adjunctive inhaled colistin should be considered, particularly for respiratory infections 1, 3
- Recommended dosing for colistin:
Sulbactam-Susceptible Acinetobacter
- For isolates with MIC ≤4 mg/L for sulbactam, ampicillin-sulbactam is recommended as an alternative to polymyxins due to its better safety profile 3
- Recommended dosing: 9-12g/day of sulbactam component in 3 daily doses as a 4-hour infusion 3
Site-Specific Considerations
Ventilator-Associated Pneumonia (VAP)
- For VAP caused by carbapenem-resistant A. baumannii, intravenous polymyxin plus adjunctive inhaled colistin is recommended 1, 3
- Nebulized antibiotics should be delivered using ultrasonic or vibrating plate nebulizers 3
- Recommended dose of nebulized colistin: 2 million IU every 8-12 hours 3
Meningitis/Ventriculitis
- For A. baumannii meningitis, intravenous antimicrobials plus intrathecal (IT) or intraventricular (IVT) administration of colistin is recommended 3
- Recommended IT/IVT dosage: 125,000 IU once daily, with consideration of a 500,000 IU loading dose 3
- Treatment duration should be approximately 3 weeks with monitoring of cerebrospinal fluid sterilization 3
Urinary Tract Infections
- Treatment duration: 7 days for uncomplicated UTIs, up to 14 days for complicated UTIs 4
- Urinary catheter removal or replacement is recommended when possible 4
Combination Therapy Considerations
- For patients with septic shock or at high risk of death, combination therapy using two antibiotics to which the isolate is susceptible is suggested 1, 5
- Combination therapy should be considered for severe infections caused by carbapenem-resistant A. baumannii 5, 2
- Avoid tigecycline monotherapy for A. baumannii infections 1, 6
- Avoid combination therapy with rifampicin and colistin, as it has not shown improved clinical outcomes 1
Empiric Therapy Considerations
- Empiric coverage for A. baumannii is recommended in:
- Severe infections during an A. baumannii outbreak
- Endemic situations
- Previously colonized patients 3
- A polymyxin should be included in empiric therapy when carbapenem-resistant A. baumannii is suspected 3
Monitoring and Adverse Effects
- Regular monitoring of renal function is essential when using polymyxins due to higher nephrotoxicity (33%) compared to ampicillin-sulbactam (15.3%) 3, 4
- Adjust polymyxin dosing in patients with renal impairment 4
- High-dose meropenem may be associated with increased risk of seizures 4
Common Pitfalls to Avoid
- Do not use aminoglycoside monotherapy for A. baumannii infections 1
- Avoid tigecycline for A. baumannii infections, particularly as monotherapy 1, 6
- Do not use carbapenems in monotherapy for severe infections in areas with high rates of resistance 3, 4
- Avoid polymyxin-meropenem combination therapy for CRAB infections with high-level carbapenem resistance (MICs >16 mg/L) 4