Clinical characteristics and outcomes of Achromobacter xylosoxidans bacteremia in critically Ill patients: an exploratory descriptive retrospective cohort study

Achromobacter xylosoxidans is an emerging opportunistic pathogen increasingly encountered in intensive care units (ICUs). Data on clinical characteristics and factors associated with outcomes remain limited. This study aimed to describe the clinical characteristics and the differences observed between survivors and non-survivors among critically ill patients with A. xylosoxidans bacteremia. This retrospective cohort study included 26 ICU patients with confirmed A. xylosoxidans bacteremia meeting Sepsis-3 criteria. Demographic characteristics, comorbidities, infection sources, disease severity scores (SOFA and APACHE II), and dynamic changes in inflammatory markers (WBC, CRP, and procalcitonin) were analyzed. The mean age was 60.7 ± 14.9 years and the overall mortality rate was 26.9%. Clinically attributed infection sources were the urinary tract (73.1%) and a presumed pulmonary source (26.9%). All deaths occurred among patients with a clinically and radiologically attributed presumed pulmonary source requiring mechanical ventilation, whereas all patients with a urinary tract source survived. However, non-survivors were also substantially older (75.7 vs. 55.2 years), had markedly higher SOFA and APACHE II scores, and had longer ICU stays. Subsequent bloodstream infection with a different pathogen, central venous catheter presence, and polymicrobial co-infection were more frequently observed in non-survivors. Post-treatment inflammatory markers decreased among survivors. In this cohort, all deaths occurred among patients with a clinically and radiologically attributed presumed pulmonary source requiring mechanical ventilation. However, these patients were also substantially older and had markedly higher disease severity scores, suggesting that the observed mortality pattern may reflect overall illness severity rather than an independent effect of the infection source.