Eradication of multidrug-resistant Acinetobacter baumannii from the respiratory tract with inhaled colistin methanesulfonate: a matched case-control study

Repeated isolation of multidrug-resistant Acinetobacter baumannii (MDRAB) from respiratory secretions poses a great challenge for infection control. We conducted a retrospective case-control study to evaluate the efficacy and adverse effect of inhaled colistin methanesulfonate (CMS) in the eradication of MDRAB from the respiratory tract. Patients who were admitted to Taipei Veterans General Hospital between February 2009 and June 2010, had at least two sets of monomicrobial culture of MDRAB from respiratory secretions, and remained in hospital for at least 14 days after the first isolation of MDRAB (index day) were included. Patients who received intravenous CMS were excluded. Patients who received CMS inhalation for ≥3 days were selected as cases whereas the controls were matched for age and Acute Physiology and Chronic Health Evaluation II score. Thirty-nine cases and controls were identified. The duration of CMS inhalation was 10.9 ± 3.6 days. The use of inhaled CMS was the only independent factor associated with the eradication of MDRAB within 14 days after the index day (OR 266.33; 95% CI 11.26–6302.18, p <0.001), and shortened the duration of MDRAB recovery from the respiratory tract by 13.3 ± 1.45 days. The adverse effects were similar for both groups. The increase of colistin minimal inhibitory concentrations in the last isolate compared with the index isolate from the same patient did not differ between the two groups. In conclusion, our study demonstrated that inhaled CMS enhanced the eradication of MDRAB from the respiratory tract without significant clinical adverse effect or impact on colistin resistance.