Colistin-based treatment for extensively drug-resistant Acinetobacter baumannii pneumonia

Data for treatment and outcomes of extensively drug-resistant Acinetobacter baumannii (XDR-AB) pneumonia are limited. A retrospective cohort study of 236 adult patients with XDR-AB pneumonia was conducted between January 2009 and December 2012. The median age of subjects was 70 years (range 17-95 years), 53% were male, 55% had ventilator-associated pneumonia and 42% had been admitted to the intensive care unit. All XDR-AB isolates were susceptible only to tigecycline and colistin; 52 (22%) of the 236 subjects did not receive an agent active against XDR-AB, with an associated 28-day survival of 0%. Colistin-based two-drug combination treatment was prescribed to 166 subjects (70%); regimens included (i) colistin and high-dose sulbactam (n=93); (ii) colistin and tigecycline (n=43); and (iii) colistin and high-dose prolonged infusion of a carbapenem (n=30). The 28-day survival rate and mean length of hospital stay were not statistically different between these three regimens (65%, 53% and 60% and 39, 39 and 38 days, respectively). Predictors of mortality included Acute Physiology and Chronic Health Evaluation (APACHE) II score [adjusted odds ratio (aOR)=1.11; P<0.001 for each point increase], duration from infection onset to receipt of active regimen (aOR=1.01; P=0.002 for each hour delay), underlying malignancy (aOR=3.46; P=0.01) and chronic kidney disease (aOR=2.85; P=0.03). These findings suggest that the three colistin-based two-drug combination regimens may be treatment options for XDR-AB pneumonia.