Severe community-acquired pneumonia still has a high incidence and mortality, but the molecular mechanism and prognostic biomarkers of severe community-acquired pneumonia caused by different pathogens are still unclear, and the best treatment strategy has not been determined. Based on this, this project intends to take patients with severe community-acquired pneumonia caused by different pathogens as the research object, explore the molecular mechanism of severe community-acquired pneumonia from multiple angles, integrate relevant research data to evaluate the rationality of initial empirical medication, and lay the foundation for precise treatment of severe pneumonia. The research results will help to develop a new rapid and accurate target for clinical diagnosis and efficacy evaluation of severe pneumonia, and build a precise treatment system for severe pneumonia.