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

Polymyxin B (PMB)-based therapy is one of the most important treatments for patients with carbapenem-resistant Acinetobacter baumanni (CRAB) caused nosocomial pneumonia. However, the optimal PMB-based combination regimen hasn't been well documented. In this retrospective study, 111 critically ill patients in intensive care unit who experienced CRAB nosocomial pneumonia and received intravenous (IV) PMB-based therapy between January 1, 2018 and June 1, 2022 were included. The primary outcome was all-cause mortality within 28 days. Cox proportional hazards 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. 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 (CB) (61.9%) or tigecycline (TC) (50.0%). In contrast, PMB + CB 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 + TC (17.9%) was higher than in other two regimens, the mortality remained highest (42.9%) and serum creatinine folds increased significantly. 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 increased risk of nephrotoxicity was observed.