Role of aerosolized colistin methanesulfonate therapy for extensively-drug-resistant Acinetobacter baumannii complex pneumonia and airway colonization

Background: Aerosolized colistin methanesulfonate (CMS) has been used for the treatment of extensively drug-resistant Acinetobacter baumannii (XDRAB) pneumonia and eradication of XDRAB colonization in the respiratory tract. The aims of this study were to compare the efficacy, adverse effects, clinical outcomes, and microbiological eradication of the cases of XDRAB pneumonia or colonization. Methods: We retrospectively reviewed the medical records of patients who received aerosolized CMS for the treatment of pneumonia and airway colonization due to XDRAB. Results: Clinical data from 118 patients were studied. The mean age of 57 patients in the pneumonia group was 79.4 years, and that of 61 patients in the colonization group was 80.0 years. Patients with XDRAB pneumonia were more likely to be ventilator-dependent than colonized patients (46.5% vs. 21.3%; p=0.005), receive steroid therapy (49.1% vs. 31.1%; p=0.046), and be admitted to an intensive care unit (ICU) at the time of aerosolized CMS treatment (56.1% vs. 32.8%; p=0.011). The in-hospital mortality rate was higher in the pneumonia group than the colonization group (50.9% vs. 33.3%; p=0.05). Microbiological eradication of XDRAB in airway samples was achieved in 75% (89 of 118) patients. In pneumonia patients, XDRAB eradication was associated with resolution or improvement of presenting symptoms and signs of infection by the end of treatment relative to the noneradicated group (57.8% vs. 25%; p=0.044), but had no influence on 30-day mortality. In colonized patients, no difference in clinical outcomes was noted between the eradicated and noneradicated groups. Conclusion: Aerosolized CMS therapy has acceptable efficacy for XDRAB pneumonia, but no proven efficacy for XDRAB airway colonization.