The Microbiological Characteristics of Acinetobacter Baumannii Associated With Early Mortality in Patients With Bloodstream Infection

Abstract

Background Despite the rapid deaths due to Acinetobacter baumannii bacteremia, the clinical impact of the microbiological characteristics of A. baumannii strains on early mortality (EM) is unclear. We aimed to identify the microbiological characteristics of A. baumannii strains associated with EM. Methods Clinical information and isolates from patients with A. baumannii bacteremia from January 2015 to December 2021 were collected. EM was defined as death within 3 d of the initial positive blood culture, whereas late mortality meant death within 5–30 d. The microbiological characteristics of A. baumannii were analyzed using multilocus sequence typing, polymerase chain reactions, and a Galleria mellonella in vivo infection model. Results Among 130 patients, 69 (53.1%) died within 30 d, and EM occurred in 38 (55.1% of 30-d deaths). Sequence type 191 (ST191) strain was more prevalent in patients with EM than in 30-d survivors (31.6% vs. 6.6%). Regarding virulence genes, bfmS was more frequent (92.1% vs. 47.5%), whereas bauA was less frequent (13.2% vs. 52.5%) in patients with EM than in 30-d survivors. Higher clinical severity, pneumonia, and ST191 infection were identified as independent risk factors for EM. In the G. mellonella infection model, ST191, bfmS+, and bauA- isolates showed higher virulence than non-ST191, bfmS-, and bauA + isolates, respectively. Conclusions ST191 and bfmS were more frequently found in the EM group. ST191 infection was also an independent risk factor for EM and highly virulent in the in vivo model. Tailored infection control measures based on these characteristics are necessary for A. baumannii bacteremia management.