Independent predictors of 28-day mortality in ICU patients with Acinetobacter baumannii versus Non-Acinetobacter baumannii gram-negative tracheal aspirate isolates

This study evaluated independent risk factors affecting 28-day mortality in intensive care unit (ICU) patients with Acinetobacter baumannii versus non-A. baumannii Gram-negative bacilli isolated from tracheal aspirate cultures. Overall, 120 ICU patients (66 males, 54 females; age: 36-94) enrolled between January 2024 and December 2025 were divided into two equal groups: the A. baumannii (n = 60) and the non-A. baumannii (n = 60). Age, sex, Charlson Comorbidity Index (CCI) score, APACHE II score, septic shock rates, and CRP levels were similar between groups (P > 0.05). However, carbapenem resistance (98.3% vs. 56.7%; P < 0.001), mechanical ventilation (MV) requirement (75.0% vs. 53.3%; P = 0.022), and 28-day mortality (63.3% vs. 40.0%; P = 0.018) were significantly higher in the A. baumannii group. ICU length of stay was significantly shorter in the A. baumannii group (16.5 vs. 26.5 days; P = 0.008), due to early-period mortality. Predominant non-A. baumannii pathogens were Klebsiella pneumoniae (51.7%) and Pseudomonas aeruginosa (35%). Multivariate logistic regression identified MV requirement (aOR: 4.706, 95% CI: 1.792-12.359, P = 0.002), A. baumannii infection (aOR: 2.512, 95% CI: 1.055-5.983, P = 0.037), and higher CCI score (aOR: 1.523, 95% CI: 1.155-2.007, P = 0.003) as independent predictors of 28-day mortality. A. baumannii isolation from tracheal aspirates and MV requirement are strong independent risk factors for 28-day mortality in ICU patients. High carbapenem resistance restricts therapeutic options and drives early mortality. Early diagnosis, rapid microbiological identification, targeted antimicrobial therapy, and strict infection control practices are paramount to improving survival outcomes in critically ill patients.