Clinical characteristics of Chlamydia psittaci pneumonia diagnosed by next-generation sequencing

Abstract

Chlamydia psittaci pneumonia is often underdiagnosed due to nonspecific presentation and limited diagnostic tools, with scarce data on the comparative utility of metagenomic next-generation sequencing (mNGS) versus targeted next-generation sequencing (tNGS) in this setting. This study aimed to characterize the clinical features of C psittaci pneumonia and provide comparative data on mNGS and tNGS, with emphasis on diagnostic accessibility, while also quantifying underreported features such as hyponatremia. A retrospective analysis was conducted on 10 patients with C Psittaci pneumonia admitted to the Department of Respiratory and Critical Care Medicine at the Second People’s Hospital of Hunan Province between January 2022 and February 2025. Clinical data, laboratory tests, imaging findings, treatment regimens, and outcomes were collected and analyzed descriptively. Among the 10 patients (6 male, 4 female; median age 70 years), 9 had underlying comorbidities and 2 had severe pneumonia. A history of avian exposure was reported in 40% of cases. All patients presented with fever (mean temperature: 39.5 ± 0.7°C), accompanied by nonspecific symptoms including cough (n = 4), chills (n = 5), anorexia (n = 5), and myalgia (n = 3). Laboratory findings revealed normal white blood cell counts in 8 cases, while lymphocytopenia, elevated inflammatory markers, abnormal liver enzymes, and hyponatremia were observed in 9 patients. Imaging predominantly showed unilateral lung consolidation (n = 5) or ground-glass opacities (n = 3), with pleural involvement in 9 cases. mNGS and tNGS were performed on bronchoalveolar lavage fluid in 5 cases each; tNGS provides a more cost-saving and rapid alternative. Post-diagnosis, treatment with moxifloxacin, doxycycline, or omadacycline for 10 to 21 days yielded generally favorable outcomes. C psittaci pneumonia is characterized by high fever and systemic symptoms, with imaging typically showing unilateral consolidation, ground-glass opacities, or mass-like lesions with pleural involvement, accompanied by liver injury, elevated inflammatory markers, and hyponatremia. Both tNGS and mNGS are effective diagnostic tools, and tNGS provides a more cost-saving and rapid alternative. Early treatment with fluoroquinolones or tetracyclines confers significant therapeutic benefits.