Clinical Features and Risk Factors for Severe Disease in 57 Cases of Chlamydia psittaci Pneumonia: A Retrospective Study

Background: This study aimed to analyze the clinical features of Chlamydia psittaci (C. psittaci) pneumonia and identify risk factors for severe patients to facilitate early diagnosis and treatment. Methods: In this retrospective analysis, we collected and summarized the clinical data of 57 patients with C. psittaci pneumonia confirmed by metagenomic next-generation sequencing (mNGS) or targeted next-generation sequencing (tNGS), who were admitted to the First Affiliated Hospital of Guilin Medical University between July 2020 and August 2025. Patients were further divided into a severe group (n=23) and a non-severe group (n=34) for comparative analysis of their clinical characteristics. Results: The mean age of the patients was 58.68 ± 12.36 years. Common symptoms included fever, cough/sputum, fatigue, dyspnea, and neurological and gastrointestinal symptoms. The severe group had a significantly higher incidence of fatigue, dyspnea, and neurological and gastrointestinal manifestations. Laboratory findings revealed that most patients had normal or mildly elevated white blood cell counts with lymphopenia, alongside significantly elevated levels of C-reactive protein (CRP), procalcitonin (PCT), and erythrocyte sedimentation rate (ESR). Anemia, hypoalbuminemia, and abnormalities in liver enzymes, myocardial enzymes, and electrolytes were also commonly observed. The predominant chest computed tomography finding was consolidation, with pleural effusion present in 59.6% of all patients and occurring more frequently in the severe group. Multivariate analysis identified CRP as an independent risk factor for severe C. psittaci pneumonia, while albumin and platelet count were protective factors. Conclusion: Pneumonia patients presenting with non-specific influenza-like symptoms should raise clinical suspicion for C. psittaci pneumonia. Particular vigilance for potential progression to severe disease is warranted in male patients, the elderly, those with underlying comorbidities, and individuals presenting with neurological or gastrointestinal symptoms. Elevated CRP, hypoalbuminemia, and thrombocytopenia serve as significant predictors of severe C. psittaci pneumonia. Keywords: Chlamydia psittaci , community-acquired pneumonia, next-generation sequencing