Early distinction between refractory M. pneumoniae pneumonia (RMPP) and non-RMPP (NRMPP) is still difficult. The community-acquired respiratory distress syndrome (CARDS) toxin can induce inflammatory and histopathological phenotypes associated with M. pneumoniae infection. This study aimed to investigate the clinical significance of CARDS toxin and pro-inflammatory cytokines in children with RMPP and to explore whether CARDS toxin can induce TNF-α expression. Levels of CARDS toxin and cytokines in BALF from control and children with MPP were determined by real-time PCR and ELISA, respectively. A receiver-operating characteristic (ROC) analysis was performed to assess the diagnostic values of CARDS toxin, TNF-α, and IL-6 in RMPP. The recombinant CARDS toxin was constructed and prepared at different concentrations for stimulation of RAW264.7 cells. After co-culture with CARDS toxin, cytokines were detected by ELISA and the mRNA levels were measured by real-time PCR. Effects of CARDS toxin and TNF-α on inflammatory cell infiltration and mucus secretion in mouse lungs were also evaluated. Levels of CARDS toxin, TNF-α and IL-6 in bronchoalveolar lavage fluid (BALF) were significantly higher in RMPP cases compared with NRMPP cases. Furthermore, TNF-α had better diagnostic ability for differentiation of RMPP with AUC of 0.824 and Youden index of 0.692 compared with CARDS toxin and IL-6. Moreover, CARDS toxin was positively correlated with TNF-α level in MPP cases. In vitro assay revealed that CARDS toxin induced RAW264.7 macrophages to secrete TNF-α. Further in vivo assay showed that TNF-α deletion partially abrogated the CARDS toxin-mediated induction of inflammatory cell infiltration and mucus secretion in mouse lungs. The high co-expression of TNF-α and CARDS toxin in BALF is a good diagnostic biomarker for differentiating children with RMPP and NRMPP.

Co-infections are common in childhood community acquired pneumonia (CAP). However, their etiological pattern and clinical impact remains inconclusive. Eight hundred forty-six consecutive children with CAP were evaluated prospectively for the presence of viral and bacterial pathogens. Nasopharyngeal aspirates were examined by direct immunofluorescence assay or polymerase chain reaction (PCR) for viruses. PCR of nasopharyngeal aspirates and enzyme-linked immunosorbent assays were performed to detect M. pneumoniae. Bacteria was detected in blood, bronchoalveolar lavage specimen, or pleural fluid by culture. Causative pathogen was identified in 70.1% (593 of 846) of the patients. The most commonly detected pathogens were respiratory syncytial virus (RSV) (22.9%), human rhinovirus (HRV) (22.1%), M. pneumoniae (15.8%). Coinfection was identified in 34.6% (293 of 846) of the patients. The majority of these (209 [71.3%] of 293) were mixed viral-bacterial infections. Age < 6 months (odds ratio: 2.1; 95% confidence interval: 1.2–3.3) and admission of PICU (odds ratio: 12.5; 95% confidence interval: 1.6–97.4) were associated with mix infection. Patients with mix infection had a higher rate of PICU admission. The high mix infection burden in childhood CAP underscores a need for the enhancement of sensitive, inexpensive, and rapid diagnostics to accurately identify pneumonia pathogens.

Background: The incidence of severe acute respiratory tract infections in children caused by Mycoplasma pneumoniae (syn. Schizoplasma pneumoniae) and Chlamydophila pneumoniae (formerly Chlamydia pneumoniae) varies greatly from year to year and place to place around the world. This study investigated the epidemiology of M. pneumoniae and C. pneumoniae infections among children hospitalized with acute respiratory infections in Suzhou, China in the year 2006, and associations between incidence rates and climatic conditions. Methods: Nasopharyngeal aspirates obtained from 1598 patients (aged 26.4 ± 28.3 months; range, 1 month to 13 years) were analyzed with real-time PCR and ELISA. Meteorological data were obtained from the weather bureau. Results: About 18.5% of patients were infected with M. pneumoniae and, C. pneumoniae, or both. Isolated M. pneumoniae infection was positively correlated with increasing age (χ² = 34.76, P < 0.0001). Incidence of M. pneumoniae infection was seasonal with a peak in summer (P < 0.0001) and minimum in winter (P = 0.0001), whereas C. pneumoniae infection was low only in autumn (P = 0.02). Monthly mean temperature was strongly correlated with the incidence of M. pneumoniae infection (r = 0.825, P = 0.001). Conclusions: M. pneumoniae and C. pneumoniae are important infectious agents in hospitalized children with acute respiratory tract infections. M. pneumoniae infection showed a strong direct correlation with environmental temperature.

The objective of this study was to assess epidemiological and clinical features of human bocavirus (HBoV) coinfection with other viruses. Children coinfected with HBoV between January 2012 and December 2014 were enrolled and retrospectively reviewed. A total of 984 patients were stratified into five groups: HBoV infection alone (n = 249), respiratory syncytial virus (RSV) infection alone (n = 649), HBoV coinfection with RSV (n = 28), with human rhinovirus (HRV) (n = 39) and with other virus (n = 19). Length of hospitalization was longer in HBoV coinfection with RSV group than HBoV (9.0 days vs. 7.0 days, p = 0.001), RSV (9.0 days vs. 8.0 days, p = 0.016) infection alone group. Pneumonia was more common in the HBoV coinfection with RSV group compared with the HBoV, RSV infection alone group, respectively (75.0% vs. 44.2%, 31.3%, p < 0.001). HBoV DNA copy numbers (383 000 copies/ml) were positively correlated with the length of hospitalization (r = 0.334, p < 0.001). HBoV coinfection with RSV increases HBoV infection severity.

Objective: To investigate the etiological characteristics of plastic bronchitis (PB) caused by pulmonary infections in children and to identify any differences in the clinical features of PB cases caused by different pathogens. Method: We collected data on children diagnosed with PB and admitted to the Respiratory Department at Soochow University Children’s Hospital between July 2021 and March 2023 utilizing electronic bronchoscopy. We analyzed clinical characteristics and the species of pathogens causing the illness in these children. Result: A total of 45 children were enrolled. The main clinical symptoms observed were cough (100%), fever (80%), shortness of breath (28.9%), and wheezing (20.0%). Pathogens were identified in 38 (84.4%) patients. Mycoplasma pneumoniae (MP) had the highest detection rate at 53.3%, followed by the Boca virus at 26.7%. MP-induced PB typically occurs in older children with an average age of 7.46 ± 2.36 years, with the main symptoms including high fever (85.7%) and local hyporespiration (42.9%). In contrast, Boca virus-induced PB tends to occur in younger children, with the main symptoms of moderate fever (54.5%), and wheezing (54.5%). The MP group exhibited a higher incidence of both internal and external pulmonary complications, including pleural effusion (42.9%), elevated aspartate aminotransferase (52.4%), lactic dehydrogenase (76.2%), and D-D dimer (90.5%). Conversely, the Boca virus group primarily showed pulmonary imaging of atelectasis (81.8%), with no pleural effusion. The average number of bronchoscopic interventions in the MP group was 2.24 ± 0.62, which was significantly higher than that required in the Boca virus group (1.55 ± 0.52). During the second bronchoscopy, 57.1% of children in the MP group still had visible mucus plugs, while none were observed in the Boca virus group. Conclusion: MP and Boca virus are the primary pathogens responsible for PB among children. The clinical manifestations of PB typically vary significantly based on the pathogen causing the condition.