Overview of patients
Of 9342 children hospitalized with pneumonia from 1st Jan 2014 to 31st Dec 2018, 593 patients with S/L-PP consisting of 398 boys and 195 girls were included in this study. The male to female ratio was about 2:1. The age of the patients with S/L-PP ranged from 1 year to 13 years (7.4±3.1years). The number of patients with S/L-PP each year was 86, 98,115,137 and 157 respectively during the study period. The annual incidence of children with S/L-PP increased with years over the study period (P<0.05). The duration of fever and cough were 4.6±2.1 days and 10.6±8.7 days respectively. 169 patients had a gasping and 208 patients had pulmonary crackles at onset. There were 149 patients with extrapulmonary manifestations including erythematous maculopapular rash, liver and kidney function lesions, and neurological complications. Only a few patients had pleural effusion. There were 383 patients with abnormal WBCs, 69 patients with abnormal ESR and 148 patients with abnormal CRP. The duration of hospital stay was 15.5±3.1 days.
Pathogen distribution with years
Table.1 summarized the distribution of pathogens with years including M. pneumoniae, respiratory syncytial virus (RSV), chlamydia pneumonia (CP), influenza A virus (IFA), parainfluenza virus (PIVS), adenovirus (ADV), Q fever Coxiella (COX), Legionella pneumophila (LP), influenza B virus (IFB), S.pneumoniae, Staphylococcus aureus (S. aureus), Pseudomonas aeruginosa (P.aeruginosa), Escherichia coli (E.coli), Klebsiella pneumoniae (K.pneumoniae), and so on. The positive rate of M.pneumoniae increased with years. The number of patients infected by M.pneumoniae was 43, 67, 96 106, and 117 each year respectively. There were significant differences in the positive rate of M.pneumoniae between the groups divided by years of patients (p<0.05). But no significant differences were found in the positive rate for other pathogens between the groups.
Age distribution of pathogens
Table.2 summarized the distribution of pathogens with age group and showed that the positive rate of M.pneumoniae increased with ages. Significant differences were observed in the positive rate of M.pneumoniae between the age groups (p<0.05). However, no significant differences were found in the positive rate of other pathogens between the age groups.
Sex distribution of pathogens
Significant differences were not observed for M. pneumoniae and S.pneumoniae between male patients and female patients. 18 patients were positive for IFB including 6 male patients and 12 female patients. Female patients displayed significantly higher positive rate for IFB than male ones. No significant difference was observed for the other pathogens between sex groups.
Season distribution of pathogens
In general, the seasonality profile of each individual pathogen was diverse. However, we did not observe distinct patterns for the pathogens.
Mixed infection types of pathogens
Co-infections with multiple pathogens were common. There were 91 patients in whom 2 or more pathogens were positive, representing 15.34% of the patients, and the types of co-infection were complex. These data indicated that 27.40% of the children with M.pneumoniae infections were co-infected with other pathogens. A total of 15 patients showed infection with 3 pathogens or more. (Table.3)
Association between pathogens and patients’ demographic and clinical characteristics
Table.4 summarized the patients’ demographic and clinical information found in association with pathogen infections. The patients groups were divided according to pathogens. Patients with co-infections of pathogens were excluded. Since the sample size was too small to obtain significance in some statistical analyses, only M. pneumoniae and S.pneumoniae were included in the statistical analyses. M.pneumoniae was statistically related to the extrapulmonary manifestations. S.pneumoniae was statistically associated with abnormal WBCs and CRPs. (Table.5)