Acinetobacter baumannii Bacteremia in China: A 10-Year Retrospective Single-Center Study of Clinical Features of Patients and Epidemiological Characteristics of Isolates

Background: Acinetobacter baumannii is an important etiology for healthcare-associated bloodstream infection (BSI) with high mortality, particularly among immunocompromised patients. At the same time, the acquisition of resistance genes and chromosomal mutations of A. baumannii has markedly reduced available treatment options. These clinical and biological features support the integrated investigation of mortality risk factors, genomic epidemiology, and the activity of new antimicrobial agents against contemporary bloodstream isolates. Methods: This retrospective single-center study enrolled 131 patients with A. baumannii BSI diagnosed in China between 2016 and 2025. We examined the clinical factors associated with in-hospital mortality and used whole-genome sequencing (WGS) to reconstruct phylogenetic relationships and to characterize the population structure, resistance genes, and virulence-associated genes. We also tested the isolates against conventional antibiotics and novel antimicrobial agents. Results: Of the 131 patients with A. baumannii BSI, 100 (76.3%) died. Multivariable Fine–Gray regression identified older age, carbapenem-resistant A. baumannii (CRAB), mechanical ventilation, and higher SOFA scores at BSI onset as independent factors associated with a higher cumulative incidence of in-hospital death. WGS showed that the bacterial population was dominated by international clone 2 (IC2), and blaOXA-23-like was the principal acquired carbapenem-resistance determinant. Conventional antimicrobial agents showed limited activity, whereas cefiderocol and sulbactam–durlobactam retained susceptibility rates of 98.5% and 80.9%, respectively. Conclusions: In this IC2-dominant cohort, older age, CRAB, mechanical ventilation, and higher SOFA scores at BSI onset were associated with in-hospital death. Cefiderocol and sulbactam–durlobactam retained substantial in vitro activity, although non-susceptible isolates were detected, supporting the need for continued genomic and phenotypic surveillance.