Clinical outcomes and safety of intravenous polymyxin B-based treatment in critically ill patients with carbapenem-resistant Acinetobacter baumannii nosocomial pneumonia

Objectives: Polymyxin B (PMB)-based therapy is one of the most important treatments for patients with nosocomial pneumonia caused by carbapenem-resistant Acinetobacter baumannii (CRAB). However, the optimal PMB-based combination regimen has not been well documented.Methods: In this retrospective study, 111 critically ill patients in the intensive care unit with CRAB noso-comial pneumonia who received intravenous PMB-based therapy between 1 January 2018 and 1 June 2022 were included. The primary outcome was all-cause mortality within 28 days. Cox proportional haz-ards regression was used to explore risk factors for mortality in the enrolled patients treated with PMB-based regimens and the three most frequent combination regimens.Results: PMB + sulbactam (SB) regimen was significantly associated with a decreased risk of mortality (aHR = 0.10, 95% CI 0.03-0.39; P = 0.001). The proportion of low-dose PMB in PMB + SB regimen (79.2%) was higher than in PMB + carbapenem (61.9%) or tigecycline (50.0%) regimens. In contrast, PMB + car-bapenem regimen significantly increased mortality (aHR = 3.27, 95% CI 1.47-7.27; P = 0.004). Although the proportion of high-dose PMB in PMB + tigecycline (17.9%) was higher than in the other two regimens, mortality remained highest (42.9%) and serum creatinine increased significantly.Conclusions: PMB in combination with SB may be a promising treatment option for patients with CRAB-induced nosocomial pneumonia, as mortality was significantly reduced with low-dose PMB and no in-creased risk of nephrotoxicity was observed.& COPY; 2023 Elsevier Ltd and International Society of Antimicrobial Chemotherapy. All rights reserved.