What is the recommended treatment for Acinetobacter infections?

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 1, 2
• Recommended dosing:
  • Imipenem: 0.5-1g every 6 hours 3
  • Meropenem: 2g every 8 hours (extended infusion recommended) 3

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
• Recommended dosing for colistin:
  • Loading dose: 6-9 million IU 1, 3
  • Maintenance: 9 million IU/day in 2-3 divided doses 1, 3

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 1
• Recommended dosing: 9-12g/day of sulbactam component in 3 daily doses as a 4-hour infusion 1

Site-Specific Considerations

Ventilator-Associated Pneumonia (VAP)

• For VAP caused by carbapenem-resistant A. baumannii, intravenous polymyxin plus adjunctive inhaled colistin is recommended 1
• Nebulized antibiotics should be delivered using ultrasonic or vibrating plate nebulizers 1
• Recommended dose of nebulized colistin: 2 million IU every 8-12 hours 1

Meningitis/Ventriculitis

• For A. baumannii meningitis, intravenous antimicrobials plus intrathecal (IT) or intraventricular (IVT) administration of colistin is recommended 1
• Recommended IT/IVT dosage: 125,000 IU once daily, with consideration of a 500,000 IU loading dose 1
• Treatment duration should be approximately 3 weeks with monitoring of cerebrospinal fluid sterilization 1

Urinary Tract Infections

• Treatment duration: 7 days for uncomplicated UTIs, up to 14 days for complicated UTIs 3
• Urinary catheter removal or replacement is recommended when possible 3

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
• Combination therapy should be considered for severe infections caused by carbapenem-resistant A. baumannii 1, 2
• Avoid tigecycline monotherapy for A. baumannii infections 1, 4
• 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 1
• A polymyxin should be included in empiric therapy when carbapenem-resistant A. baumannii is suspected 1

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%) 1, 3
• Adjust polymyxin dosing in patients with renal impairment 3
• High-dose meropenem may be associated with increased risk of seizures 3

Common Pitfalls to Avoid

• Do not use aminoglycoside monotherapy for A. baumannii infections 1
• Avoid tigecycline for A. baumannii infections, particularly as monotherapy 1, 4
• Do not use carbapenems in monotherapy for severe infections in areas with high rates of resistance 1, 3
• Avoid polymyxin-meropenem combination therapy for CRAB infections with high-level carbapenem resistance (MICs >16 mg/L) 3