Mortality due to carbapenem-resistant Acinetobacter baumannii bacteraemia: a 5-year cohort study in intensive care patients.

Abstract

Objectives: Carbapenem-resistant Acinetobacter baumannii (CRAB) has emerged as a major and difficult-to-treat nosocomial pathogen. This study estimated the mortality associated with CRAB bacteraemia in patients receiving treatment in the intensive care unit. A susceptible-infection counterfactual framework was applied to reflect the potential benefit of improved antimicrobial therapy.

Methods: A 5-year (2019-2023) cohort study was conducted in a tertiary-care referral hospital in Greece. Competing risks survival analysis methods were applied to estimate excess in-hospital mortality because of CRAB bacteraemia by comparing patients infected by CRAB with those infected by other more susceptible Gram-negative bacteria (GNB).

Results: The cohort comprised 400 intensive care patients with GNB bacteraemia (median age 70 years, 65% man). CRAB was the most common pathogen (43%), followed by Klebsiella pneumoniae (12%), Escherichia coli (11%), and Pseudomonas aeruginosa (10%). Patients with CRAB bacteraemia experienced significantly higher in-hospital mortality at 14 days (35% vs. 21%), 28 days (53% vs. 30%), and overall (74% vs. 52%) than patients with other GNB bacteraemia. Multivariable competing risks regression confirmed that CRAB bacteraemia was independently associated with an increased risk of 28-day inpatient death (cause-specific hazard ratio: 1.80, 95% CI: 1.28-2.54; sub-distribution hazard ratio: 1.84, 95% CI: 1.28-2.62), simultaneously lowering the probability of discharge alive (cause-specific hazard ratio: 0.68, 95% CI: 0.38-1.21; sub-distribution hazard ratio: 0.52, 95% CI: 0.30-0.91). Estimation of the attributable fraction suggested that effective antimicrobial management may result in a relative decrease in the risk of in-hospital mortality by 44% (95% CI: 22-61%) in patients with CRAB bacteraemia.

Discussion: CRAB's detrimental role as a leading cause of increased inpatient mortality and prolongation of hospitalization in intensive care patients was demonstrated. These outcomes could improve substantially if more effective antimicrobial treatment becomes available. Nevertheless, considering that CRAB is predominantly a hospital-acquired pathogen, efforts should always be directed towards preventing nosocomial transmission.