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Objective <p>To investigate differences in alveolar lavage fluid pathogen spectrum, T lymphocyte subsets, and prognosis between patients with severe pneumonia with and without acute respiratory distress syndrome (ARDS).</p> Methods <p>A retrospective cohort study was conducted, enrolling 160 patients with severe pneumonia admitted to our hospital between April 1, 2021, and April 1, 2025. Among them, 80 patients had ARDS (ARDS group) and 80 did not (Non-ARDS group). Bronchoalveolar lavage fluid (BALF) was collected for t-NGS pathogen detection, T lymphocyte subset analysis, and 28-day prognosis assessment.</p> Results <p>1. Pathogens Profile: The ARDS group exhibited significantly higher BALF prevalence of <i>Escherichia coli</i> (15.0% vs 2.5%, P = 0.005), <i>Enterococcus faecium</i> (22.5% vs 5.0%, P = 0.001), and <i>Candida albicans</i> (25.0% vs 10.0%, P = 0.013) were significantly higher than in the Non-ARDS group. 2. Immunological Characteristics: In the entire cohort, the ARDS group exhibited significantly lower counts of total T lymphocytes, CD4+, and CD8+ T cells. After excluding patients with viral infections, only the CD8+ T cell count remained significantly different (P = 0.041). 3. Prognosis: The 28-day mortality rate was significantly higher in the ARDS group than in the Non-ARDS group (Log-rank P &lt; 0.001), with a 3.77-fold increased risk of death (HR = 3.77, 95% CI: 1.98–7.15). 4. Risk Factors: Multivariable Cox regression analysis across the entire cohort identified vasoactive drug use, <i>Escherichia coli</i> and <i>Candida albicans</i> infections, and elevated CD4+/CD8+ ratios as independent risk factors for mortality. After excluding patients with viral infections, the independent risk factors shifted to vasoactive drugs, <i>Escherichia coli</i>, CRP, and AST. Detailed hazard ratios with confidence intervals are presented in the Results section.</p> Conclusion <p>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 (<i>E. coli</i>, 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, <i>E. coli</i> infection, systemic inflammation (CRP), and liver injury (AST). This study provides evidence for precise risk stratification and personalized treatment.</p>

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

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年11月29日

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  • Dong-Xue Rao,
  • Xin-Yue Sun,
  • Rong Chen

摘要

Objective

To investigate differences in alveolar lavage fluid pathogen spectrum, T lymphocyte subsets, and prognosis between patients with severe pneumonia with and without acute respiratory distress syndrome (ARDS).

Methods

A retrospective cohort study was conducted, enrolling 160 patients with severe pneumonia admitted to our hospital between April 1, 2021, and April 1, 2025. Among them, 80 patients had ARDS (ARDS group) and 80 did not (Non-ARDS group). Bronchoalveolar lavage fluid (BALF) was collected for t-NGS pathogen detection, T lymphocyte subset analysis, and 28-day prognosis assessment.

Results

1. Pathogens Profile: The ARDS group exhibited significantly higher BALF prevalence of Escherichia coli (15.0% vs 2.5%, P = 0.005), Enterococcus faecium (22.5% vs 5.0%, P = 0.001), and Candida albicans (25.0% vs 10.0%, P = 0.013) were significantly higher than in the Non-ARDS group. 2. Immunological Characteristics: In the entire cohort, the ARDS group exhibited significantly lower counts of total T lymphocytes, CD4+, and CD8+ T cells. After excluding patients with viral infections, only the CD8+ T cell count remained significantly different (P = 0.041). 3. Prognosis: The 28-day mortality rate was significantly higher in the ARDS group than in the Non-ARDS group (Log-rank P < 0.001), with a 3.77-fold increased risk of death (HR = 3.77, 95% CI: 1.98–7.15). 4. Risk Factors: Multivariable Cox regression analysis across the entire cohort identified vasoactive drug use, Escherichia coli and Candida albicans infections, and elevated CD4+/CD8+ ratios as independent risk factors for mortality. After excluding patients with viral infections, the independent risk factors shifted to vasoactive drugs, Escherichia coli, CRP, and AST. Detailed hazard ratios with confidence intervals are presented in the Results section.

Conclusion

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.