This study was a prospective multicenter cohort of severe pneumonia. And by collecting clinical samples to clarify the correlation between lung microbiome, intestinal microbiome, host susceptibility, and prognosis of severe pneumonia patients.

The human lung and intestinal microbiota play an important role in human health. At present, the correlation between lung and intestinal microbiota in severe pneumonia patients and host susceptibility is limited to small sample, single center studies. Due to sample size limitations, the pathogenesis of severe pneumonia caused by many pathogens remains unclear. This study plans to construct sputum, alveolar lavage fluid, feces, and whole blood samples of severe pneumonia patients admitted to the ICU from 2023 to 2025, and collect clinical data from patients to identify changes in lung and intestinal microbiome, host susceptibility, and disease progression risk in different groups of patients.

Inclusion Criteria:

1. New lung infection that meets one of the following definitions: the patient receives mechanical ventilation (invasive or non-invasive) due to acute respiratory failure, with a PEEP level of 5cm or above; Patients receiving high flow oxygen therapy with a FiO2 of 50% or more and a PaO2: FiO2 ratio below 300

Exclusion Criteria:

1. Expected length of stay in ICU is less than 1 day
2. Pregnant

Overall, the investigators will include all severe pneumonia patients transferred to the ICU, including community acquired pneumonia, hospital acquired pneumonia, and ventilator-associated pneumonia.

Under the permission of Chinese law, if a researcher needs an IPD, the investigators can share the IPD.