Clinical features，diagnosis，and treatment of chlamydia psittaci pneumonia based on metagenomic next-generation sequencing: an analysis of 15 cases

Abstract:

Objective To investigate the clinical features，diagnosis and treatment，and prognosis of rare chlamydia psittaci pneumonia，and to improve the understanding of this disease in related clinical fields.Methods A retrospective analysis was performed for the clinical data of 15 patients who were diagnosed with chlamydia psittaci pneumonia in The First Affiliated Hospital of Gannan Medical University from January 2017 to December 2022，and the clinical features，diagnosis，and key points for differential diagnosis were summarized and analyzed. Meanwhile，related articles in China and globally were searched to systematically discuss the latest advances in the diagnosis and treatment of chlamydia psittaci pneumonia.Results Among the 15 patients with chlamydia psittaci pneumonia included in this study，there were 10 male patients（66.67%） and 5 female patients（33.33%），with an aged of 62（32-79） years. Among these patients，14（93.33%） had poultry contact history，8（53.3%） had the history of underlying diseases，and 5（33.33%） developed severe pneumonia. Among the 15 patients，8 had normal white blood cell count（WBC）（53.3%），5 had elevated WBC（33.3%），and 2（13.3%） had a reduction in WBC；9（60.0%） had normal hemoglobin，and 6（40.0%） had a reduction in hemoglobin；13（86.7%） had an increase in the percentage of neutrophils； all patients（100.0%） had a significant increase in C-reactive protein；13（86.67%） had an increase in procalcitonin，and 12（80.0%） had an increase in lactate dehydrogenase；11（73.33%） had abnormal liver function，8（53.33%） had abnormal renal function，and 6（40.0%） had abnormal coagulation function；13（86.7%） had electrolyte disturbance. In addition，arterial blood gas analysis showed varying degrees of reduction in the partial pressure of blood oxygen in 11 patients（73.33%），and 8 patients（53.33%） had an oxygenation index lower than 300 mmHg； 4 patients（26.67%） had no obvious dyspnea and thus did not undergo arterial blood gas analysis. All patients in this study underwent bronchoscopy，with bronchoalveolar lavage fluid obtained for metagenomic next-generation sequencing（mNGS），and all patients were infected with multiple pathogens besides chlamydia psittaci. All 15 patients underwent lung CT and other imaging examinations，among whom 7（46.67%） had unilateral pulmonary consolidation and 8（53.33%） had bilateral pulmonary consolidation；9 patients（60.0%） also had pleural effusion，and some of them showed various imaging findings，including consolidation opacities，ground-glass opacities，mass opacities，reversed halo sign，and mediastinal and hilar lymph node enlargement. All 15 patients with chlamydia psittaci pneumonia received standard anti-infective therapy after diagnosis，and among the 5 patients with severe pneumonia，2 received ECMO adjuvant therapy. No treatment-related adverse reactions or adverse events were observed，with a mean length of hospital stay of 13.9 days. No death was observed，and all patients were discharged after improvement.Conclusion Chlamydia psittaci pneumonia lacks specific clinical features and manifestations and tends to develop into severe exacerbation，and mNGS detection of bronchoalveolar lavage fluid can help to achieve an accurate diagnosis. Early administration of tetracycline and quinolone antibiotics can improve the prognosis of patients to the greatest extent.