Comparison of the efficacy of colistin monotherapy and colistin combination therapies in the treatment of nosocomial pneumonia and ventilatorassociated pneumonia caused by Acinetobacter baumannii

Abstract

Objective. To investigate whether there was a difference in mortality, clinical response and bacterial eradication between colistin monotherapy and colistin combination therapies for the treatment of nosocomial pneumonia/ventilator-associated pneumonia (VAP) caused by Acinetobacter baumannii in a medical intensive care unit (ICU). Methods. This retrospective, observational and single-centre study included all patients who were in the medical ICU of Gazi University Medical Faculty Hospital and diagnosed with nosocomial pneumonia/VAP caused by A. baumannii between January 2009 and September 2014. Results. The median age of the 134 patients was 68 years and 53.3% were male. The most common causes of admission were respiratory insufficiency (66.7%) and sepsis/septic shock (54.8%). In patients with nosocomial pneumonia/VAP caused by A. baumannii, on median day 5 of admission, colistin monotherapy was used in 23 (21.6%) patients, a carbapenem combination was used in 80 (59.7%) patients, sulbactam-ampicillin combination was used in 42 (31.4%) patients, tigecycline combination was used in 26 (19.4%) patients, and sulbactam-cefoperazone combination was used in 17 (12.7%) patients. Median ICU stay of the patients was 15.5 days, and 112 (83.6%) patients died. Colistin monotherapy and combination therapies had no superiority over each other in clinical response for the treatment of A. baumannii-associated nosocomial pneumonia/VAP. Mortality was found to be higher in patients receiving the colistin-carbapenem combination (64.3% v. 36.4%, p=0.016). Discharge/day-of-death Sequential Organ Failure Assessment score (odds ratio (OR) 2.017, 95% confidence interval (CI) 1.330 - 3.061) and vasopressor use (OR 9.014, 95% CI 1.360 - 59.464) were independent risk factors for ICU mortality.Conclusion. Colistin monotherapy and combination therapies have no superiority over each other for clinical response in the treatment of nosocomial pneumonia/VAP caused by multidrug-resistant A. baumannii. Colistin-SAM was associated with improved microbiological eradication and colistin-carbapenem combination was associated with increased mortality.