Treatment of Acinetobacter baumannii Wound Infections

Introduction to Treatment Guidelines

The American College of Physicians recommends ampicillin-sulbactam as the preferred treatment for Acinetobacter baumannii wound infections when the isolate is susceptible to sulbactam (MIC ≤4 mg/L), administered as a 4-hour infusion of 3g of sulbactam every 8 hours (9-12g/day total), due to its superior safety profile and comparable efficacy to polymyxins 1, 2

In areas with low carbapenem resistance (<25%), carbapenems (imipenem, meropenem, doripenem) are the treatment of choice for Acinetobacter baumannii skin and soft tissue infections 1, 2
The recommended dose of imipenem is 0.5-1g every 6 hours (extended infusion is not possible due to drug instability) 1
The recommended dose of meropenem is 2g every 8 hours (caution: high doses are associated with an increased risk of seizures) 1

Ampicillin-sulbactam is the preferred option for carbapenem-resistant Acinetobacter baumannii (CRAB) with an MIC of sulbactam ≤4 mg/L, with a dosing regimen of 3g of sulbactam every 8 hours as a 4-hour infusion (9-12g/day total) 1, 2
Sulbactam has intrinsic activity against Acinetobacter baumannii independent of its beta-lactamase inhibitor properties 2
Compared to colistin, ampicillin-sulbactam has lower nephrotoxicity (15.3% vs 33%) with comparable clinical cure rates 1, 2

Colistin (polymyxin E) is an alternative treatment option, with a loading dose of 6-9 million IU and a maintenance dose of 4.5 million IU every 12 hours in critically ill patients with a creatinine clearance >50 mL/min 1, 3
Polymyxin B is an alternative to colistin, with a loading dose of 2-2.5 mg/kg and a maintenance dose of 1.5-3 mg/kg/day in 2 doses 1

Tigecycline may be considered only for approved indications (complicated skin and soft tissue infections) with secondary bacteremia, with a standard regimen of a 100mg loading dose followed by 50mg every 12 hours 4, 5
For severe infections, a high-dose regimen of 200mg loading dose followed by 100mg every 12 hours should always be used in combination therapy 4, 5, 1

For severe wound infections with CRAB, combination therapy with two active in vitro agents is recommended 1, 2
Recommended combinations include colistin + high-dose carbapenem, colistin + sulbactam + tigecycline, or sulbactam/polymyxin + a second agent (tigecycline, rifampicin, or fosfomycin) 1, 2

For uncomplicated wound infections, 7-10 days of treatment is generally sufficient 3
For complicated or systemic infections, treatment may be extended up to 14 days based on clinical response 2, 3

Renal function monitoring is mandatory, with nephrotoxicity occurring in up to 33% of patients receiving colistin 1, 2
More frequent monitoring is necessary with polymyxins compared to sulbactam (15.3% nephrotoxicity) 1