Targeted NGS diagnosis of Chlamydia psittaci pneumonia

We describe two cases of severe community-acquired pneumonia with pleural effusion. A 52-year-old woman and a 64-year-old woman presented with high fever, cough, and systemic symptoms. Initial laboratory findings revealed marked elevation of inflammatory markers (hs-CRP, IL-6, ESR) with normal or mildly elevated white blood cell counts. Empirical broad-spectrum antibiotic therapy was ineffective in both patients. Chest CT scans demonstrated unilateral pulmonary consolidations accompanied by small ipsilateral pleural effusions. Comprehensive conventional microbiological tests, including stains, cultures, and serology for common respiratory pathogens, returned negative. Bronchoalveolar lavage fluid (BALF) analysis using mp-tNGS rapidly identified C. psittaci (with 142 and 251 reads per 100,000 sequencing reads, respectively), with a mean turnaround time of 11.35 hours. Epidemiological history revealed exposure to pigeons and a bird market. Targeted therapy with doxycycline led to rapid clinical improvement, resolution of fever, and significant radiographic clearance