ABSTRACT
@#Abstract: Objective To analyze the clinical characteristics of Chlamydia psittaci pneumonia and improve the diagnosis and treatment skills of clinicians on this disease. Methods The clinical data of thirty-nine Chlamydia psittaci pneumonia cases detected by metagenomic next-generation sequencing (mNGS) from September 2020 to January 2022 at the Affiliated Hospital of Southwest Medical University were retrospectively analyzed. Results There was a history of poultry exposure in 89.7%(35 cases) of the patients. The most common clinical manifestations were high fever (92.3%, 36), cough (76.9%,30), muscle soreness (48.7%,19), headache (38.5%,15), etc. Laboratory examinations showed 76.9% of patients had a normal leukocyte count, and 76.9% had decreased lymphocyte count, often accompanied by elevated C-reactive protein (100%), procalcitonin (97.4%), interleukin-6 (95.8%), interleukin-10 (95.8%), alanine aminotransferase (74.4%), and aspartate aminotransferase (84.6%). Univariate analysis indicated that there were statistically significant differences in the levels of aspartate transaminase, blood urea nitrogen, C-reactive protein, and procalcitonin between severe pneumonia patients and non-severe pneumonia patients（P<0.05）. Multivariate logistic regression analysis showed that an elevated blood urea nitrogen (OR=4.899) had guiding significance for predicting the occurrence of severe pneumonia. Bronchoscopy examination showed no abnormalities in 53.6% of the patients. The imaging manifestations of pulmonary lesions were mainly lobar pneumonia (61.5%) and air bronchograms (94.9%). Therapeutically, it was sensitive to tetracyclines, macrocyclic lactones, and fluoroquinolones. A total of 84.6%(33 cases) of the patients were cured and discharged from the hospital at the end of the treatment. Conclusion Chlamydia psittaci pneumonia is a zoonotic disease that can be detected by mNGS. An elevated blood urea nitrogen level has guiding significance for predicting the occurrence of severe pneumonia. Empirically-selected regimens based on doxycycline are effective for the treatment of Chlamydia psittaci pneumonia.