Clinical characteristics of patients infected with Chlamydia pneumoniae in Beijing from 2015 to 2019

Objective: To aralyze the clinical characteristics of Chlamydia pneumoniae infection in Beijing. Methods: Based on Beijing Respiratory Pathogen Surveillance System, acute respiratory infection patients were recruited from 35 different types of sentinel hospitals in Beijing. Their epidemiological and clinical data were systematically collected and clinical specimens were also obtained. Nuclear acid testing was performed for 30 types of respiratory pathogens (including Chlamydia pneumoniae). The identified patients of Chlamydia pneumoniae infection were divided into two groups, the acute upper respiratory tract infection (AURI) group and pneumoniae group. The differences in clinical characteristics, laboratory examination and prognosis were compared by using independent sample t test, Mann-Whitney U test, χ2 test or Fisher's exact probability test. Results: A total of 119 patients of Chlamydia pneumoniae infection were included, including 12 patients in the AURI group and 107 patients in pneumoniae group. Chlamydia pneumoniae infection mainly occurred in people aged from 5 to 44 years, accounting for 81.5% (97/119). The three most common clinical symptoms were cough (92.4%, 110/119), fever (88.8%, 95/107), and sputum production (76.5%, 91/119). White blood cell counts increased in 39.3% (46/117) of patients. Neutrophile granulocyte proportion increased in 39.7% (46/116) of patients. Platelet count increased in 36.9% (41/111) of patients. An increase of the creatine kinase MB isoenzyme (CKMB) was observed in 12 pneumonia patients (24.5%, 12/49). Radiological examination showed that 90.6% (87/105) of patients in the pneumoniae group had pulmonary parenchymal changes; the lesion occurred most commonly in the lower right lung lobe (34.3%, 36/105) and the lower left lung lobe (27.6%, 29/105). Although 73.8% (79/107) of patients in the pneumoniae group were hospitalized, no case received intensive care unit or mechanical ventilation. As to outcomes, one patient developed respiratory failure and 6 patients suffered myocardial injury. No death was observed in this study. The median days of hospitalization and course of illness for pneumonia patients M(P25,P75) were 10.0 (7.0, 13.0) days and 18.0 (13.5, 22.0) days, respectively. Conclusion: Generally, Chlamydia pneumoniae infections in Beijing from 2015 to 2019 were mild, and the main clinical manifestations were cough, fever and sputum. However, most patients in the pneumoniae group caused by Chlamydia pneumoniae still required hospitalization but with a better outcome.