Rapid diagnosis of Chlamydia psittaci pneumonia with pleural effusion using multiplex PCR‑based targeted next‑generation sequencing: A case report

Chlamydia psittaci pneumonia (CPP) is a zoonotic disease with non‑specific clinical and radiographic features, complicating timely diagnosis. Although not common, pleural effusion may indicate more severe disease. Conventional diagnostic methods lack the sensitivity and speed. The present report highlights the utility of multiplex PCR‑based targeted next‑generation sequencing (mp‑tNGS) for rapid etiological diagnosis of CPP, particularly in patients with pleural effusion. A 52‑year‑old woman and a 64‑year‑old woman both presented with high fever, cough and systemic symptoms. Inflammatory markers (hs‑CRP, IL‑6 and ESR) were found to be markedly elevated with normal or mildly elevated white blood cell counts. A chest CT exhibited unilateral consolidations with small ipsilateral pleural effusions. Conventional microbiological tests (stains, cultures and serology) were negative. Bronchoalveolar lavage fluid mp‑tNGS rapidly identified Chlamydia psittaci (142 and 251 reads per 100,000 sequencing reads, respectively), with a mean turnaround time of 11.35 h (from laboratory receipt to result). Epidemiological history revealed exposure to pigeons and a bird market. Doxycycline therapy led to rapid clinical improvement, fever resolution and notable radiographic clearance. Therefore, pleural effusion can be a feature of CPP and may indicate more severe disease. mp‑tNGS proved rapid and decisive when conventional methods failed, enabling timely targeted therapy. A high index of suspicion combined with mp‑tNGS is thus key in accurately diagnosing and improving prognosis.