Does Early Concordant Antibiotic Treatment Reduce Mortality Among Hospitalized Patients with Carbapenem-Resistant Acinetobacter baumannii Bacteremia? A Retrospective Cohort Study

Carbapenem-resistant <i>Acinetobacter baumannii</i> (CRAB) bacteremia is a critical health concern associated with high morbidity and mortality and limited treatment options. Whether early initiation of concordant antibiotic therapy upon recognition of sepsis improves outcomes remains unclear. <b>Methods</b>: We conducted a retrospective cohort study of 413 patients diagnosed with CRAB bacteremia to evaluate the impact of early concordant antibiotic treatment (i.e., administration of in vitro active antibiotics within 24 h of blood culture collection) on 30-day mortality. Multivariable logistic regression was conducted to identify predictors of early concordant treatment and to evaluate its association with 30-day mortality. To address potential confounding by early death, a sensitivity analysis was performed which included only patients who survived at least 48 h after blood culture collection. <b>Results</b>: Among the study cohort, 30% (122/413) received early concordant treatment (all received colistin), while 70% (291/413) received early discordant treatment. The median age of patients receiving early concordant treatment was 69 (interquartile range (IQR), 62-78) years vs. 71 (IQR, 62-81) years in the discordant group (<i>p</i> = 0.1). Patients who received early concordant treatment were more likely to be mechanically ventilated (52% vs. 40%, <i>p</i> = 0.03) and have rectal carriage of multidrug-resistant bacteria (16% vs. 9%, <i>p</i> = 0.06). The 30-day mortality was 63% (260/413). In univariate analysis, survivors were more likely to have received early concordant treatment (38% vs. 25%, <i>p</i> = 0.005); however, this association was not statistically significant in the multivariable model (adjusted odds ratio [aOR] 0.36, 95% confidence interval [CI] 0.13-1.02, <i>p</i> = 0.053). Significant factors associated with 30-day mortality included age ≥65 years (aOR 4; 95% CI 1.1-17, <i>p</i> = 0.04) and SOFA score ≥5 points (aOR 7.14; 95% CI 2-25, <i>p</i> < 0.01). In the sensitivity analysis limited to patients who survived at least 48 h after blood culture collection, early concordant treatment remained unassociated with 30-day mortality (aOR 1.8; 95% CI 0.5-7, <i>p</i> = 0.4). <b>Conclusions</b>: Early concordant antibiotic treatment was not significantly associated with 30-day mortality in patients with CRAB bacteremia. Older age and SOFA score were significant predictors of mortality. Whether this finding reflects the limited efficacy of colistin, which was the predominant empiric antibiotic in this cohort, remains unclear; nevertheless, more effective therapeutic options for CRAB bacteremia are urgently needed to improve patient outcomes.