[Etiology of severe community-acquired pneumonia in immunocompromised patients]

Objective: To analyze the etiology of severe community-acquired pneumonia (SCAP) in immunocompromised patients, and to investigate the relationship between underlying diseases and infectious microorganisms. Methods: A retrospective analysis was performed on SCAP in immunocompromised patients admitted to the Fourth Department of Respiratory and Critical Medicine (MICU) of China-Japan Friendship Hospital from January 1, 2017 to December 31, 2019. A total of 119 SCAP patients were finally enrolled, including 65 males (54.6%), with an average age of (59.3±14.5) years. The average of Sequential Organ Failure Assessment (SOFA) score was 6.7±3.6 and the acute physiology and chronic health evaluation (APACHE) Ⅱ score was 19.4±6.8. Sixty (50%) of these patients were finally improved and discharged. Long-term glucocorticoid treatment was the main risk factor for immunocompromise. The difference of pathogenic microorganisms between patients with and without structural lung diseases, and the influence of different pathogenic microorganisms on hospital mortality were calculated, respectively. P<0.05 was considered to be statistically significant. Results: In this study, 99 (83.2%) patients were identified to have positive etiological results, and the incidence of concurrent infection was 54.5%. The top three pathogens were Pneumocystis Jiroveci (55.6%), Cytomegalovirus (47.5%) and Aspergillus (23.2%). Staphylococcus aureus was the most common bacterium, followed by Pseudomonas aeruginosa and Klebsiella pneumoniae. The risk of Pneumocystis Jiroveci infection was significantly higher in patients without underlying lung diseases as compared to those with underlying lung diseases (64.3% vs. 44.2%, P = 0.046). The in-hospital mortality was not different among patients infected with different pathogens(all P>0.05), but was higher in those with mixed infections(56.7% vs. 33.9%, P=0.013). Conclusions: Pneumocystis Jiroveci and Cytomegalovirus were the most common pathogens in immunocompromised patients with severe community-acquired pneumonia, and the incidence of Pneumocystis Jiroveci was significantly higher in patients without underlying lung diseases.