Clinical Experience with Tigecycline in the Treatment of Carbapenem-Resistant Acinetobacter Infections

Tigecycline is a promising therapeutic option against many current multidrug resistant pathogens. The aim of this retrospective study was to determine the clinical and microbiological outcomes of patients treated with tigecycline for serious infections caused by carbapenem-resistant Acinetobacter calcoaceticus-Acinetobacter baumannii complex (Acb-complex). A retrospective study was conducted to define the patients who received tigecycline for carbapenem-resistant Acb-complex infections between 1 June, 2008 and 1 May, 2009. A total of 21 patients were eligible for the study. The median age of the patients was 48 years and 6 patients were female. Eighteen patients were treated with tigecycline for carbapenem-resistant Acb-complex as the sole microorganism while 3 received it for polymicrobial infections. All Acb-complex isolates were susceptible to tigecycline. The most common indication of tigecycline treatment was surgical-site infections (SSI) followed by ventilator associated pneumonia (VAP). Tigecycline was the sole antibiotic administered in 7 patients while concurrent antibiotics were used in 14 patients. The median duration of tigecycline therapy was 14 days. Two patients died within 14 days of initiating treatment, representing an attributable mortality rate of 9.5% while 4 patients died within 30 days representing a crude mortality rate of 19.1%. Seventeen out of 21 patients had successful clinical outcomes, cure in 11 patients and improvement in 6. Fourteen of 21 patients had microbiological failure. Correlation between microbiological response with clinical outcome was poor. Clinical failure was more common in patients with VAP. Patients with bacteremia were more likely to have microbiological failure while microbiological outcome was better in patients with SSI. In this retrospective study, 81% (17 of 21) of the patients infected with carbapenem-resistant Acb-complex had a positive outcome under tigecycline therapy. However, these preliminary results should be evaluated cautiously in the absence of well-controlled studies.