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Metagenomic-based quantification of Pseudomonas aeruginosa burden links microbiome collapse to mortality in severe community-acquired pneumonia.

BACKGROUND: Severe community-acquired pneumonia (sCAP) remains a major cause of mortality in critically ill patients, Pseudomonas aeruginosa (P. aeruginosa) is a frequent pathogen associated with poor prognosis in this population. While metagenomic next-generation sequencing (mNGS) is widely used for pathogen detection, its value in quantifying pathogen abundance and linking it to lung microbiome alterations remains unclear. OBJECTIVES: This study investigated the association between P. aeruginosa abundance quantified by mNGS and lung microbiome alterations and clinical outcomes in sCAP patients. METHODS: This multicenter retrospective study included 130 patients with sCAP caused by P. aeruginosa from five hospitals (September 2021-June 2025). Patients were stratified into low, medium, and high abundance groups according to mNGS-derived reads per ten million (RPTM) values of P. aeruginosa. Lung microbiome diversity and community structure were analyzed, and differences between groups were assessed using appropriate statistical methods. The association between P. aeruginosa abundance and clinical outcomes was evaluated using correlation analysis, sankey diagram, receiver operating characteristic curve, grey zone analysis and logistic regression. RESULTS: A total of 130 patients with sCAP due to P. aeruginosa were stratified into low, medium, and high abundance groups based on mNGS-derived RPTM value. Microbial diversity decreased progressively with increasing abundance, and community structures differed significantly among groups (all P&#x2009;<&#x2009;0.05). P. aeruginosa became increasingly dominant, accounting for up to 95.99% of the microbiota in the high abundance group. Higher P. aeruginosa abundance was associated with increased disease severity, including longer mechanical ventilation, prolonged hospital stay, and higher 28-day mortality. Sankey diagram showed a progressive decline in treatment effectiveness and an increase in mortality with increasing P. aeruginosa abundance. P. aeruginosa_RPTM showed moderate predictive value for mortality (AUC&#x2009;=&#x2009;0.761, Sens&#x2009;=&#x2009;69.40%, Spec&#x2009;=&#x2009;75.30%, cutoff: 41122, grey zone: 2287-220339) and remained independently associated with 28-day mortality in multivariable analysis [2.219 (1.509 to 3.262), P&#x2009;<&#x2009;0.001]. CONCLUSION: In patients with sCAP, higher P. aeruginosa_RPTM measured by mNGS was associated with reduced lung microbiome diversity and unfavorable clinical outcomes. RPTM-based risk stratification may help identify patients at increased risk of poor prognosis.

Humans

Effect of Metagenomic Next-Generation Sequencing on Clinical Outcomes of Patients With Severe Community-Acquired Pneumonia in the ICU: A Multicenter, Randomized Controlled Trial.

BACKGROUND: Metagenomic next-generation sequencing (mNGS) was previously established as a method that can increase the pathogen identification rate in patients with severe community-acquired pneumonia (SCAP). RESEARCH QUESTION: What is the impact on clinical outcomes of mNGS of BAL fluid (BALF) in patients with SCAP in the ICU? STUDY DESIGN AND METHODS: A multicenter randomized controlled open-label clinical trial was conducted in 10 ICUs. Patients were randomized in a 1:1 ratio to undergo BALF assessment with conventional microbiological tests (CMTs) only (ie, the CMT group) or BALF assessment with both mNGS and CMTs (ie, the mNGS group). The primary outcome was the time to clinical improvement, defined as the time from randomization to either an improvement of two points on a six-category ordinal scale or discharge from the ICU, whichever occurred first. RESULTS: A total of 349 patients were randomized to treatment between January 1, 2021, and November 18, 2022; 170 were assigned to the CMT group and 179 to the mNGS group. In the intention-to-treat analysis, the time to clinical improvement was better in the mNGS group than in the CMT group (10&#xa0;days vs&#xa0;13&#xa0;days; difference, -2.0&#xa0;days; 95%&#xa0;CI, -3.0 to 0.0&#xa0;days). Similar results were obtained in the per-protocol analysis. The proportion of patients with clinical improvement within 14&#xa0;days was significantly higher in the mNGS group (62.0%) than in the CMT group (46.5%). There was no significant difference in other secondary outcomes. INTERPRETATION: We found that compared with the use of CMTs alone, mNGS combined with CMTs reduced the time to clinical improvement for patients with SCAP. CLINICAL TRIAL REGISTRATION: Chinese Clinical Trial Registry, ChiCTR; www.chictr.org.cn/index.html; ChiCTR2000037894.

Humans

Corticosteroids in ARDS: old controversies, new insights, and future directions.

Corticosteroids modulate key inflammatory and fibroproliferative pathways involved in ARDS through genomic and non-genomic glucocorticoid receptor signaling. Advances in ARDS pathophysiology have highlighted the importance of timing, inflammatory burden, and host response in determining treatment efficacy. Clinical evidence supports corticosteroid use in moderate-to-severe ARDS, particularly in COVID-19 ARDS and severe community-acquired pneumonia, with reductions in mortality and duration of mechanical ventilation. However, treatment effects remain heterogeneous across etiologies and biological subphenotypes. Recent identification of hyperinflammatory and hypoinflammatory ARDS phenotypes suggests that corticosteroid responsiveness is not uniform. Hyperinflammatory phenotypes and septic ARDS appear more likely to benefit, whereas evidence remains limited or conflicting in influenza-associated and non-septic ARDS. Long-term effects and adverse outcomes, including metabolic complications and ICU-acquired weakness, remain insufficiently characterized. Future research is increasingly focused on precision medicine approaches integrating biomarkers, adaptive platform trials, and phenotype-guided strategies. Emerging developments include lung-targeted corticosteroid delivery systems and selective glucocorticoid receptor modulators designed to improve efficacy while reducing systemic toxicity. Corticosteroids should therefore be considered a context-dependent therapy whose benefit is influenced by etiology, disease stage, inflammatory phenotype, and timing of administration.

Humans

Longitudinal clinical proteomics reveals pneumonia type-specific protein biomarkers and autoantibodies.

Community-acquired pneumonia is a major cause of morbidity and mortality globally. Specific molecular endotypes are currently not well defined, and different viral or bacterial pathogens may trigger specific host responses and pathogenic mechanisms. We performed longitudinal proteomic profiling of bronchoalveolar lavage fluid and plasma from bacterial, influenza, and SARS-CoV-2-driven pneumonia. Our analysis revealed highly pneumonia type-specific proteomic signatures, including COVID-19-specific antibodies locally produced in the lung. These antibodies showed biased immunoglobulin V-domain usage, linked to a CD69/CD83 plasma cell state associated with disease severity and degree of autoimmunity. Using mass spectrometry-driven autoantibody profiling in 2 independent COVID-19 cohorts, we identified 177 putative autoantibodies targeting extracellular matrix, nuclear, and immune-related proteins. Of note, temporal changes in autoantibody profiles correlated with clinical markers of inflammation, organ dysfunction, and duration of hospitalization. These findings highlight the autoimmune aspects of COVID-19 and provide potential biomarkers and therapeutic targets to help improve patient outcomes.

Humans