Mortality risk factors in patients with bloodstream infections due to multidrug-resistant Gram-negative bacilli

This study aimed to analyze risk factors for mortality in hospitalized patients with bloodstream infections caused by multidrug-resistant Gram-negative bacilli in a retrospective cohort (January-December 2022).

Hospitalized patients with positive monomicrobial blood cultures for GNB (from central venous catheters and peripheral venipuncture) were included. Medical records and blood culture isolates were reviewed. The primary endpoint was all-cause mortality at ≤ 30 days. Risk factor analysis was performed using univariate models, survival curves (Cox regression), and an adjusted Cox proportional hazards model.

A total of 126 patients with Gram-negative bacillus bloodstream infection were included, 36 of them died within ≤ 30 days, representing a mortality rate of 28.6%. Of these deaths, 32/36 (88.9%) were due to carbapenem-resistant bacilli. The most frequently isolated gram-negative bacilli were: Acinetobacter baumannii, Pseudomonas aeruginosa, and Klebsiella pneumoniae. According to the univariate analysis, mortality was 13.2 times higher (95% CI 4.3-40.5; p = 0.000) in patients with carbapenem-resistant bacilli and 4.2 times higher (95% CI 1.8-9.6; p = 0.001) in those with carbapenem-resistant A. baumannii. The main factors associated with all-cause mortality within ≤ 30 days were: age ≥46 years, infection with carbapenem-resistant bacilli, ineffective empirical treatment, and septic shock.

Having received ineffective empirical treatment was an independent predictor of mortality, with a hazard ratio (HR) of 10.2 (95% CI: 2.6-39.9; p = 0.001). Mortality due to bloodstream infection was related with a high frequency of patients with isolated infection by carbapenem-resistant gram-negative bacilli, mainly A. baumannii (CRAB).