Comparing ceftazidime/avibactam and polymyxin B for treating carbapenem-resistant organisms infections: a propensity score-matched retrospective cohort study

•The outcome benefits of the CAZ/AVI group were different before and after matching.•No advantage of CAZ/AVI group over PMB group in mortality and clinical response.•The CAZ/AVI-based regimen is superior to PMB-based regimen in CRO eradication and in treating CRPA infections.•The CAZ/AVI monotherapy is more effective than PMB monotherapy in treating CRO infections.•The occurrence of nephrotoxicity was comparable between the CAZ/AVI and PMB groups. Comparative studies of Ceftazidime/avibactam(CAZ/AVI) versus polymyxin B (PMB) for carbapenem-resistant organisms (CRO) infections are limited. We aims to compare the efficacy and safety of CAZ/AVI and PMB in treating CRO infections. This single-center, propensity score-matched (PSM) retrospective cohort study involved adult patients with CRO infections. Patients who received a CAZ/AVI-based regimen were included in the cohort group, while those prescribed with a PMB-based regimen were in the control group. The primary outcome was 28-day all-cause mortality. Among 298 eligible patients, 96 patients in each group were included in the PSM cohort. The CAZ/AVI group showed no improvement in 28-day or 14-day all-cause mortality, nor in 14-day clinical response, compared to the PMB group. However, the CAZ/AVI-based regimen showed higher 14-day clinical response rates than PMB-based regimen in subgroups of carbapenem-resistant Pseudomonas aeruginosa (CRPA) infections and monotherapy. The CAZ/AVI group achieved more CRO eradication than the PMB group (crude OR 1.658; 95% CI, 1.108-2.480; P=0.014; adjusted OR 1.718; 95% CI, 1.055-2.798; P=0.030). This advantage in CRO eradication with CAZ/AVI was consistent in most subgroups including septic shock, bloodstream infection and lower respiratory tract infection. The CAZ/AVI and PMB groups had comparable nephrotoxicity (crude OR 0.577; 95% CI, 0.306-1.089; P=0.090, adjusted OR, 0.741; 95% CI, 0.361-1.521; P= 0.414). CAZ/AVI-based and PMB-based regimens demonstrated similar clinical efficacy and nephrotoxicity in treating CRO infections. However, CAZ/AVI was superior to PMB in CRO eradication and treating CRPA infections. CAZ/AVI monotherapy was more effective than PMB monotherapy for CRO infections. ChiCTR2300078790 prospectively registered on Dec 19, 2023 (https://www.chictr.org.cn). [Display omitted]