ABSTRACT
Objective To explore the diagnosis and clinical characteristics of atypical severe pneumonia caused by Chlamydia abortus(C.abortus).Methods Clinical data of 4 patients diagnosed with atypical severe pneumonia caused by C.abortus in a hospital from January 2021 to November 2022 were collected.Clinical characteristics,dia-gnosis and treatment,and precautions of the disease were comprehensively analyzed.Results All 4 patients were male,aged 63-73 years old,with acute onset,high fever,cough and expectoration.Three patients had a history of contact with poultry,one patient had a history of contact with abortion goat.The interval between the emerging of clinical symptoms and the onset of acute respiratory failure in 4 patients was 1-6 days,and the oxygenation index(PaO2/FiO2)at admission was less than 200 mmHg,which gradually decreased with the progression of the disease,active support with a ventilator was necessary.Two patients had an increase in white blood cell count,4 had an in-crease in neutrophil percentage,3 had a mild decrease in platelet count.Among 4 patients,2,2,3 and 4 patients showed elevated levels of aspartate aminotransferase,alanine aminotransferase,creatine kinase,and serum creati-nine respectively,2 patients had mild hyponatremia,4 patients showed significant increase in C-reactive protein,procalcitonin,and interleukin-6 levels.Four patients'chest CT findings showed main involvement of single or mul-tiple lung lobes,with exudation and consolidation,and later involvement of multiple lobes of lung.The metageno-mic next-generation sequencing of bronchoalveolar lavage fluid detected the DNA sequence of C.abortus.Based on the clinical manifestations,contact history,chest CT,and metagenomic next-generation sequencing results of 4 pa-tients,the diagnosis was C.abortus.atypical severe pneumonia.After timely adjustment of the treatment of anti-in-fection regimen based on doxycycline,the patients'condition improved and were discharged.Conclusion C.abor-tus may also cause human pneumonia,which can lead to serious clinical outcome after infection.Patient had a histo-ry of animal contact should be alert to such diseases.Metagenomic next-generation sequencing can detect C.abortus.