To investigate the characteristics and clinical characteristics of respiratory pathogens in hospitalized children with community acquired pneumonia (CAP), and analyze their correlation with the concentration of air pollutant PM2.5.

Sputum specimens from 1192 hospitalized children at Children's Hospital of Zhengzhou University from January 2019 to December 2020 were collected, and nine clinically common respiratory pathogens were detected by fluorescent quantitative PCR, including Streptococcus pneumoniae (SP), Escherichia coli (EC), Staphylococcus aureus (SA), Haemophilus influenzae (HI), Streptococcus pneumoniae (LP), Streptococcus pneumoniae (PA), Klebsiella pneumoniae (KP), Mycoplasma pneumoniae (MP), and Chlamydia pneumoniae (CP). Air PM2.5 concentrations in Zhengzhou were recorded in real time.

The total detection rate for pathogens was 42.6%; the most common Gram-positive organism was SP and the most common Gram-negative organism was HI. Among the four seasons, the detection rate was the highest in winter. Among the lower respiratory pathogens of pneumonia in children, the detection rates for SP and HI were higher in the infant and toddler group than in the preschool and school-age groups, while the detection rate for MP was higher in the school-age group than in the infant and toddler and preschool groups (P＜0.05). The detection rates for SP, PA, and MP were significantly higher in the mechanically ventilated patients with severe pneumonia than in the non-mechanically ventilated patients with severe pneumonia and patients with mild pneumonia (P＜0.05). When comparing single SP, PA, and MP infections in children with severe pneumonia, it was found that there were statistically significant differences in the clinical manifestations of cough, shortness of breath/dyspnea, laboratory results of CK-MB and ALT, and pulmonary consolidation and pleural effusion on pulmonary imaging (P＜0.05). PM2.5 concentrations of air pollutants were fluctuating during the investigation period, and PM2.5 concentrations were positively correlated with SP, HI, MP, and PA detection rates (r=0.858, 0.673, 0.723, and 0.591, respectively; P＜0.05 for all).

SP, HI, and MP are important pathogens among children with CAP in Zhengzhou, with high detection rates in infants and children. The detection rate is highest in winter and lowest in summer among the four seasons. The severity of pneumonia caused by different pathogens as well as clinical features, laboratory tests, and imaging manifestations differ, and their detection rates are closely related to the concentrations of air pollutants PM2.5.