Clinical Characteristics ，Treatment and Prognosis of Twenty-two Patients with Chlamydia psittaci pneumonia Diagnosed by Metagenomic Next-Generation Sequencing
Authors: Chu Weili , Jia Junli , Huang Lisha , Sheng Yanbing , Xu Aiguo , Xing Lihua , Gao Jing 
Published: October 2023

Abstract
Objective To analyze the clinical characteristics, imaging, laboratory examination，treatment and prognosis of Chlamydia psittaci (C. psittaci) pneumonia, so as to improve the early diagnosis and treatment of this disease.
Methods A retrospective analysis obtained from the First Affiliated Hospital of Zhengzhou University from September 2019 to June 2022 was performed. The epidemiological characteristics, clinical manifestations, laboratory tests, imaging features, treatment and prognosis of 22 patients with C. psittaci pneumonia confirmed by of Metagenomic next-generation sequencing (mNGS).
Results Among the 22 patients, 13 (59.09%) were males and 9 (40.91%) were females, ranging in age from 25 to 81 years old, with an average age of (59.73±12.04) years. 14 patients had a history of contact with poultry or birds. The common symptoms were fever (22/22, 100%), cough (15/22, 68%), fatigue (11/22, 50%), dyspnea (9/22, 41%), expectoration (7/22, 32%), headache (9/16, 56%).The median number of white blood cells (WBC)was within the normal range, C-reactive protein (CRP), procalcitonin (PCT), Creatine kinase (CK), Lactate dehydrogenase (LDH), Aspartate aminotransferase (AST), D-dimer and Fibrinogen (FIB) were significantly increased. CT scan showed consolidation (22/22,100%), Multilobular distribution (11/22, 50%) and pleural effusion (6/22, 27%).According to CURB-65 score, 22 patients were divided into severe group and non-severe group. Compared with non-severe patients, CRP increased more significantly in severe patients (P<0.01).The percentage of neutrophils, neutrophil lymphocyte ratio (NLR)，PCT, LDH and CK increased significantly in severe patients (P<0.05), while the platelet（PLT）decreased significantly (P<0.05). All 22 patients were diagnosed by mNGS, and the time from onset to diagnosis was 5 days. Doxycycline regimen is effective and the temperature of 15 patients (68.2%) returned to normal within 3 days. Among the 22 patients, 5 patients received invasive mechanical ventilation, including 2 patients treated with Veno-veno extracorporeal membrane oxygen (VV-ECMO) and 2 patients developed septic shock and required vasoactive drug treatment. These five patients were Death at follow-up after automatic discharge. Of the remaining 17 patients, 1 received non-invasive mechanical ventilation and 3 received high-flow humidified oxygen therapy. The remaining 17 patients recovered.
Conclusions C. psittaci pneumonia is an atypical community-acquired pneumonia (CAP) caused by C. psittaci infection. The characteristic clinical manifestations of C. psittaci pneumonia are high fever, fatigue, lobar pneumonia, normal WBC count and elevated inflammatory indicators. The symptoms of severe patients are not typical, but laboratory results can provide some clues. mNGS technology can detect C. psittaci early, reduce unnecessary antibiotic use. The treatment effect of doxycycline is significant, and most patients have a good prognosis, but if the patient's condition is severe and invasive mechanical ventilation is required, the prognosis is poor.
Fundprogram: Joint project of Medical Science and Technology Project of Henan Province in 2020(LHGJ20200316)