The goal of this longitudinal observational study is to investigate the pathogen spectrum composition of severe pneumonia (SP) in different disease stages and to study the changes of immune inflammatory factors in patients with SP in different course of disease during and after the COVID-19 pandemic. The main questions it aims to answer is:

What is the pathogenic profile of SP patient admitted in intensive care unit (ICU) during and after COVID-19 pandemic? What is the dynamic pattern of etiology and immunoinflammatory factors of SP progression during the period in ICU? Are those indexes mentioned above associated with the prognosis of SP?

This is a multi-center, longitudinal, observational study.

Participants

SP patients will be continuously recruited in ICU department in Shanghai General Hospital and respiratory-specific ICU (RICU) department in the First Affiliated Hospital of Chongqing Medical University during June 1, 2022 to December 31, 2024.

The investigators applied the AmericanThoracic Society(ATS)/Infectious Diseases Society of America (IDSA) major criteria to a cohort of patients hospitalized in two tertiary hospitals with severe pneumonia in order to describe its epidemiology, microbiology, and outcomes.

Assessment of disease progression

1. Shock: Definition: A systemic pathological process in which the effective circulating blood volume is reduced due to various reasons and the tissue microcirculation perfusion is seriously insufficient, resulting in cell damage and serious dysfunction of function and metabolism of important organs. Overall arterial pressure decline: systolic blood pressure less than 90mmHg or mean arterial pressure (MAP) less than 70mmHg, accompanied by tachycardia. Clinical signs of hypoperfusion: skin damp cold with vasoconstriction and cyanosis; Kidney urine volume is less than 0.5ml/kg/h; The nervous system includes changes in mind (dullness of reaction, loss of orientation and confusion). Hyperlactacidemia: greater than 2mmol/L.
2. Invasive mechanical ventilation: (1) Definition: Support of ventilation and improvement of oxygenation by inserting an intubation tube into the trachea and delivering warm, fully oxygenated, and moist gases to the airways and lungs at pressures above atmospheric pressure. (2) Classification: invasive ventilator-assisted ventilation under tracheal intubation, invasive ventilator-assisted ventilation under tracheal incision.
3. High fever: body temperature (armpit temperature) exceeds 39 ° C. (Note: High fever is generally defined at 38.5℃ in clinical practice.)
4. The above symptoms persist: shock for more than 3 days, high fever for more than 3 days, mechanical ventilation for more than 1 week.

Indicators

1. Sociodemographic indexes: sex, age, personal history
2. Clinical indicators: clinical diagnosis, past history, present history, treatment history, laboratory examination, clinical prognosis
3. Laboratory examination : culture, species of infectious agent, antibiotic susceptibility test Microbiological etiological identification methods include: ① oral and pharyngeal swabs: polymerase chain reaction (PCR) for COVID-19 nucleic acid; ② Nasopharyngeal swab: PCR for influenza A virus nucleic acid; ③ Rectal swab: Macconkey plate + drug-sensitive paper was used to detect the presence of carbapenem-resistant gram-negative bacillus, and loop-mediated isothermal amplification was used to identify the presence of IPM, VIM, NDM, KPC, OXA and other resistance genes. ④ Smear: Various specimens are diluted and stained to observe whether there are bacteria and fungi and their morphology; ⑤ Culture: microbial culture of various specimens, and drug sensitivity test to determine drug resistance; ⑥ Quick test: Rapid detection of infectious diseases, including 17 bacteria and 7 fungi; ⑦ Immunofluorescence staining: Use fluorescein to label fungal cell wall, observe fungal morphology under fluorescence microscope for qualitative detection; ⑧ Next generation sequencing (NGS).

Other laboratory tests: Blood routine (white blood cell count, neutrophil count, lymphocyte count and neutrophil-to-lymphocyte ratio (NLR), C-reactive protein (CRP), procalcitonin (PCT)).

Inclusion Criteria:

• At least 18 years of age
• Clinical diagnosed of severe pneumonia (case definition: adults according to "Diagnosis and Treatment of Adults with Community-acquired Pneumonia"-- An Official Clinical Practice Guideline of the American Thoracic Society and Infectious Diseases Society of America, 2019)
• Have at least one microbiological test result

Exclusion Criteria:

• No data of clinical prognosis

Severe pneumonia patients admitted in ICU department in Shanghai General Hospital and respiratory-specific ICU department in the First Affiliated Hospital of Chongqing Medical University during June 1, 2022 to April 28, 2024.

The datasets used in this study are available upon request to the principle investigator.