Clinical outcomes and safety of polymyxin B versus tigecycline combination therapy for pneumonia of carbapenem-resistant : a retrospective cohort study.

Purpose: Infection by carbapenem-resistant (CRKP) has high mortality. There is no clear optimal therapeutic choice for pneumonia caused by CRKP. The aim of this study was to compare the clinical outcomes and safety of the standard doses of polymyxin B-based regimens vs tigecycline-based regimens and to identify risk factors for mortality.

Methods: This retrospective cohort study included patients with pneumonia caused by CRKP between January 1, 2020 and December 31, 2022. The primary outcomes were 7-day bacterial eradication rate and 14- and 28-day all-cause mortality. The secondary outcome was incidence of acute kidney injury.

Results: Seventy-three patients were included in this study, 29 in the polymyxin B-based combination therapy group and 44 in tigecycline-based combination therapy group. There were no significant differences between the two groups in terms of the 7-day bacterial eradication rate (31.03% vs 20.45%,  = 0.409), the 14-day all-cause mortality (37.93% vs 22.73%,  = 0.160), and the incidence of acute kidney injury (14.29% vs 6.82%,  = 0.526). The 28-day all-cause mortality in the polymyxin B-based therapy group was higher than in the tigecycline-based group (75.86% vs 45.45%,  = 0.010). Binary logistic regression analysis revealed that male and previous use of carbapenems were independent factors associated with 28-day all-cause mortality for patients treated with polymyxin B ( < 0.05).

Conclusions: Polymyxin B-based combination therapy at the standard dose should be used with caution for patients with CRKP-induced pneumonia, especially for men who used carbapenems prior to CRKP detection.