Characteristics of Chlamydia pneumoniae infection in 141 children with respiratory tract infection and risk factors for severe pneumonia

Purpose Literature on Chlamydia pneumoniae infection in children is far less abundant than that on Mycoplasma pneumoniae infection. This study aims to describe the characteristics of Chlamydia pneumoniae (C. pneumoniae) respiratory tract infection in children and to identify the risk factors for cases with severe pneumonia. Methods Data of 141 children with C. pneumoniae respiratory tract infection were collected from a university tertiary hospital from June 2019 to April 2025. Patients were divided into 3 groups: non-pneumonia ( N = 64), pneumonia ( N = 47) and severe-pneumonia groups ( N = 30). Differences among groups were compared of demographic, clinical, biochemical and radiological data. Risk factors for severe C. pneumoniae pneumonia (CPP) were analyzed using multivariate binary logistic regression analysis. Results Data of 141 children (61 males and 80 females) with a median age of 8.0 years (interquartile range 6.7–9.9) were collected. C. pneumoniae respiratory tract infection peaked in winter (58/141, 41.1%) in school-aged children (≥7.0 years old, 99/141, 70.2%) with major clinical manifestations being cough (135/141, 95.7%) and fever (69/141, 48.9%). Radiological manifestations included patchy opacities and consolidation in the pneumonia group and pleural effusion, lobar pulmonary consolidation, pulmonary atelectasis and “white lung” like changes (diffuse bilateral pulmonary opacification) in the severe-pneumonia group. Median time of hospital stay was 8.0 days in pneumonia group and 15.0 days in severe-pneumonia group, respectively. Multivariate binary logistic regression identified elevated wheezing (OR = 15.468, 95% CI: 2.845–84.101, P = 0.002) and coinfection (OR = 8.253, 95% CI:1.763–38.630, P = 0.007) as factors for severe CPP. Conclusions Respiratory tract infection of C. pneumoniae in children mainly occurs in winter in school-aged children with cough and fever being the major clinical manifestations. Wheezing and coinfection are associated with severe CPP in children, suggesting potential roles in risk stratification.