Clinical outcomes of colistin in combination with either 6-G sulbactam or carbapenems for the treatment of extensively drug-resistant acinetobacter baumannii pneumonia with high MIC to sulbactam, a prospective cohort study

Abstract

Purpose: Extensively drug-resistant Acinetobacter baumannii (XDRAB) is an important cause of nosocomial pneumonia with limited therapeutic options. Colistin-based regimen is the recommended treatment. Which drugs should be combined with colistin remains uncertain. The aim of this study was to investigate the clinical outcomes of patients with XDRAB pneumonia who were treated with colistin, combined with either 6-g sulbactam or carbapenems, in the setting of high MIC to sulbactam. Patients and methods: In this prospective cohort study, hospitalized patients diagnosed with XDRAB pneumonia in Phramongkutklao Hospital were enrolled. The primary outcome was 28-day mortality. Secondary outcomes were 7- and 14-day mortality, length of stay, ventilator days and factors associated with mortality. Results: From 1 July 2016 to 30 September 2017, 182 patients were included; 92 received colistin plus sulbactam and 90 received colistin plus carbapenems. Most of the patients were males diagnosed with ventilator-associated pneumonia in medical intensive care unit. Overall mortality rates at 7, 14, 28 days were 24.2%, 37.4%, and 53.3%, respectively. Mortality rates did not differ between sulbactam group and carbapenem groups at 7 days (19.6% vs 28.9%, p-value 0.424, adjusted HR 1.277; 95% CI = 0.702-2.322), 14 days (34.8% vs 40%, p = 0.658, adjusted HR 1.109; 95% CI = 0.703-1.749) and 28 days (51.1% vs 55.6%, p = 0.857, adjusted HR 1.038; 95% CI = 0.690-1.562). Length of stay, ICU days and ventilator days did not differ. Complications of treatment including acute kidney injury were not statistically different. Conclusion: In XDRAB pneumonia with high MIC to sulbactam, differences in mortality rates were not statistically significant between colistin plus 6-g sulbactam and colistin plus carbapenems.