Clinical Features of 186 Cases of Chlamydia psittaci Pneumonia: A Multicenter Study

Chlamydia psittaci pneumonia is an uncommon type of pneumonia characterized by non-specific clinical manifestations. Current knowledge regarding its clinical features is insufficient. Therefore, we aimed to elucidate its epidemiological profile, clinical characteristics, and distinctions between severe and non-severe cases.

Clinical data of 186 patients diagnosed with C. psittaci pneumonia using next-generation sequencing (NGS) were systematically collected from seven hospitals in Guangdong Province, China, between January 2019 and June 2025. Epidemiological characteristics, clinical presentations, laboratory results, chest computed tomography (CT) features, bronchoscopy findings, and treatment outcomes were analyzed, with comparisons by disease severity.

Of 186 patients (58.1% male, 50-74 years), 43.5% presented with severe disease, and 67.2% developed complications. Most cases occurred during autumn or winter (67.2%), and a history of bird or poultry exposure was reported in 68.3%. Prevalent clinical symptoms included fatigue (98.9%), high fever (90.3%), and headache (73.7%). Laboratory findings showed elevated serum levels of C-reactive protein, procalcitonin, fibrinogen, and D-dimer in most patients (over 90%). Additionally, over 70% had increased neutrophilia, alanine transaminase, aspartate transaminase, and lactate dehydrogenase levels, with reduced lymphocyte counts. Chest CT findings frequently revealed pulmonary consolidation (100%), ground-glass opacities (97.8%), and air bronchograms (81.2%). Severe cases showed extensive bilateral and multilobar consolidation, with increased prevalence of pleural and pericardial effusions. The median time from admission to diagnosis was 3 (2-4) days, with 96.2% of patients improving following targeted antimicrobial therapy and being discharged, while 3.2% died.

C. psittaci pneumonia is characterized by a high incidence of severe cases and both intrapulmonary and extrapulmonary complications. Its clinical manifestations are diverse and multifaceted, with hallmark features including high fever, relative bradycardia, normal white blood cell counts, elevated transaminases, and pulmonary consolidation. Early diagnosis through NGS and targeted antimicrobial therapy are associated with positive patient outcomes.