Treatment of Acinetobacter Infections

General Treatment Principles

• The Infectious Diseases Society of America recommends treatment of Acinetobacter infections based on antimicrobial susceptibility testing, with carbapenems as first-line therapy for susceptible isolates and polymyxins for carbapenem-resistant strains 1, 2

Treatment Algorithm Based on Susceptibility

• For carbapenem-susceptible Acinetobacter, carbapenems are the drugs of choice, with recommended dosing of imipenem 0.5-1g every 6 hours and meropenem 2g every 8 hours (extended infusion recommended) 3, 4
• For carbapenem-resistant Acinetobacter, intravenous polymyxin is strongly recommended, with adjunctive inhaled colistin considered for respiratory infections 1, 5

Site-Specific Considerations

• For ventilator-associated pneumonia caused by carbapenem-resistant A. baumannii, intravenous polymyxin plus adjunctive inhaled colistin is recommended, with nebulized antibiotics delivered using ultrasonic or vibrating plate nebulizers 1, 5
• For A. baumannii meningitis, intravenous antimicrobials plus intrathecal or intraventricular administration of colistin is recommended, with a treatment duration of approximately 3 weeks 5

Combination Therapy Considerations

• Combination therapy using two antibiotics to which the isolate is susceptible is suggested for patients with septic shock or at high risk of death, and for severe infections caused by carbapenem-resistant A. baumannii 1, 7

Empiric Therapy Considerations

• Empiric coverage for A. baumannii is recommended in severe infections during an outbreak, endemic situations, and in previously colonized patients, with a polymyxin included in empiric therapy when carbapenem-resistant A. baumannii is suspected 6, 8

Monitoring and Adverse Effects

• Regular monitoring of renal function is essential when using polymyxins due to higher nephrotoxicity, with adjustment of polymyxin dosing in patients with renal impairment 4, 6
• High-dose meropenem may be associated with an increased risk of seizures 4

Common Pitfalls to Avoid

• Aminoglycoside monotherapy should not be used for A. baumannii infections, and tigecycline should be avoided, particularly as monotherapy 1
• Carbapenems should not be used in monotherapy for severe infections in areas with high rates of resistance, and polymyxin-meropenem combination therapy should be avoided for CRAB infections with high-level carbapenem resistance 4, 8