Bacteremia Caused by Acinetobacter baumannii: Epidemiologic Features, Antimicrobial Susceptibility, and Outcomes

Acinetobacter baumannii bacteremia is becoming more prevalent and is associated with increasing morbidity and mortality. Escalating antibacterial resistance further contributes to therapeutic dilemmas, enhanced infection control support and poorer outcomes in patients infected with these bacteria. A retrospective analysis of patients whose blood cultures produced A. baumannii from January 2007 through January 2013 was performed. Data regarding the epidemiologic features, antimicrobial susceptibility and outcomes of patients with A. baumannii bacteremia were collected and analyzed. Sixty A. baumannii isolates each from a different patient were identified. The Charlson Comorbidity Index (≥3) was the greatest among patients with multi-drug resistance (MDR) compared to intermediate drug resistance (IDR) and pan-sensitive (PS) A. baumannii. The mean APACHE II scores for MDR, IDR and PS A. baumannii bacteremia were 21, 15 and 11, respectively (P < 0.05, MDR v. PS). Seventy-three percent of the isolates were resistant to quinolones, 44% to piperacillin/tazobactam, 45% to amikacin, 22% to imipenem, 0% to ticarcillin/clavulanate, and 0% to polymyxin. Among 28 patients with MDR A. baumannii bacteremia, 20 received inadequate empiric treatment, and 16 of these patients died (80%). Of the remaining eight patients with MDR bacteremia who received adequate empiric antibiotics, only two died (25%). The severity of underlying illness, degree of antibiotic resistance and receiving inadequate initial antibiotic therapy are associated with mortality among patients with bacteremia due to A. baumannii.