Abstract
BACKGROUND: Few studies comprehensively reported the clinical characteristics, prognosis, and factors associated with severe disease in patients with confirmed Chlamydia psittaci pneumonia identified by metagenomic next-generation sequencing (mNGS). METHODS: This retrospective study included 63 patients with Chlamydia psittaci pneumonia diagnosed by mNGS. The clinical characteristics and prognosis were analyzed. Cox regression was used to identified factors associated with severe cases. RESULTS: A total of 63 patients were confirmed with detected Chlamydia psittaci DNA by mNGS in the bronchoalveolar lavage fluid or blood. A total of 16 (25.4%) patients had severe disease. The overall in-hospital mortality was 4.7% (3/63), with a rate of 18.7% (3/16) in the severe group. 90.4% (57/63) of patients were older than 50 years. 21 (33.3%) patients had poultry/bird exposure. The most common symptoms included fever (100%), cough (63.5%) and fatigue (63.5%). All patients showed lung consolidation (100%) on chest CT, with air bronchograms (96.8%) and pleural effusion (41.3%). In the multivariable Cox regression, the levels of hs-CRP (P = 0.003), creatinine (P = 0.002), and presence of bilateral lung infection (P = 0.003) were independent factors associated with severe pneumonia. CONCLUSION: Psittacosis pneumonia predominantly affects middle-aged and elderly adults. Elevated levels of hs-CRP and creatinine, the presence of bilateral lung involvement associated with progression to severe disease. Psittacosis-induced severe pneumonia is associated with high mortality. CLINICAL TRIAL NUMBER: Not applicable.