Analysis of pathogen spectrum in bronchoalveolar lavage fluid, T lymphocyte depletion, and prognosis in patients with severe pneumonia complicated by ARDS

Patients with severe pneumonia complicated by ARDS exhibit a distinct gut-derived pathogen spectrum and T-cell immune exhaustion, associated with poorer outcomes. Mortality risk in the full cohort was independently associated with vasoactive drug use, specific pathogen infections (E. coli, Candida albicans), and immune dysregulation (elevated CD4+/CD8+ ratio). In the non-viral infection subgroup, core immune deficiency manifested as specific depletion of CD8+ T cells, and mortality drivers shifted to vasoactive drug use, E. coli infection, systemic inflammation (CRP), and liver injury (AST). This study provides evidence for precise risk stratification and personalized treatment.