BACKGROUND: It is unclear whether the responses of refractory and common Mycoplasma pneumoniae (MP) pneumonia to macrolides differ. Hence, this study aimed to identify biomarkers that may be used to distinguish refractory and common pneumonias caused by MP in children at hospital admission.
METHODS: The study included 123 children divided into five groups according to infection agent and treatment protocol: Group I included those with MP infection without documented viral infection, treated with only macrolides; Group II included those with MP infection without documented viral infection, treated with a combination of macrolides and methylprednisolone; Group III included those with MP infection and documented viral infection, treated with only macrolides; Group IV included those with viral pneumonia without documented MP infection; Group V was the control group composed of admitted children without MP or a documented viral infection. These five groups were further subdivided into Groups A (including Groups I, III, IV, and V) and B (Group II) according to the responses to macrolide treatment. Concentrations of cytokines interleukin 6, interleukin 17, interleukin 18, and tumor necrosis factor-α, and lactate dehydrogenase, and ferritin of all children were evaluated, and these levels were compared among the groups. Statistical comparisons were made using Kruskal Wallis test and Mann-Whitney U test.
RESULTS: Serum lactate dehydrogenase, interleukin 18, and ferritin concentrations were significantly higher in Group II than in Groups I, III, IV, and V and were significantly higher in Group B than in Group A. When the serum lactate dehydrogenase concentration was 350 IU/L or higher, the sensitivity and specificity for diagnosing refractory MP pneumonia were 73 and 80%, respectively. When the interleukin 18 level was 360 pg/mL or higher, the sensitivity and specificity for diagnosing refractory MP pneumonia were 93 and 70%, respectively. When the ferritin level was 230 pg/mL or higher, the sensitivity and specificity for diagnosing refractory MP pneumonia were 67 and 67%, respectively.
CONCLUSIONS: These results suggest that serum lactate dehydrogenase, interleukin 18, and ferritin constitute the critical combination of biomarkers useful for predicting refractory MP pneumonia in children at hospital admission.

To examine prospectively the radiographic clearance of refractory Mycoplasma pneumoniae pneumonia (RMPP) in immunocompetent children, and to identify independent predictors of time to complete radiographic resolution in patients with RMPP.
A prospective cohort study.
Children\'s Hospital of Soochow University, China.
A total of 187 patients with RMPP treated with bronchoscopy were prospectively enrolled in the study between January 2012 and December 2015.
Serial chest radiographs were obtained after discharge every 4 weeks up to a maximum of 24 weeks after diagnosis or until large infiltration on chest radiographs had resolved. Multivariate logistic regression was performed to identify independent predictors of time to complete radiographic resolution.
Of the 187 patients with RMPP, bronchial mucus plug formation was detected in 73 (39.0%). C reactive protein (CRP) ≥50 mg/L, lactate dehydrogenase (LDH) ≥480 U/L, total fever duration ≥10 days and presence of mucus plugs were associated with longer time to radiographic clearance (all p<0.01). Compared with children without mucus plugs, those with mucus plugs were significantly more likely to have longer time to radiographic clearance (adjusted OR: 11.5; 95% CI 2.5 to 45.7; p<0.01).
Clinicians might use duration of fever, CRP, LDH and presence of mucus plugs as parameters to identify children at a longer time to radiographic clearance in patients with RMPP.

Mycoplasma pneumoniae (MP) is a leading cause of community-acquired pneumonia in children and young adults. Although MP pneumonia is usually benign and self-limited, in some cases it can develop into life-threating refractory MP pneumonia (RMPP). However, the pathogenesis of RMPP is poorly understood. The identification and characterization of proteins related to RMPP could provide a proof of principle to facilitate appropriate diagnostic and therapeutic strategies for treating paients with MP. In this study, we used a quantitative proteomic technique (iTRAQ) to analyze MP-related proteins in serum samples from 5 patients with RMPP, 5 patients with non-refractory MP pneumonia (NRMPP), and 5 healthy children. Functional classification, sub-cellular localization, and protein interaction network analysis were carried out based on protein annotation through evolutionary relationship (PANTHER) and Cytoscape analysis. A total of 260 differentially expressed proteins were identified in the RMPP and NRMPP groups. Compared to the control group, the NRMPP and RMPP groups showed 134 (70 up-regulated and 64 down-regulated) and 126 (63 up-regulated and 63 down-regulated) differentially expressed proteins, respectively. The complex functional classification and protein interaction network of the identified proteins reflected the complex pathogenesis of RMPP. Our study provides the first comprehensive proteome map of RMPP-related proteins from MP pneumonia. These profiles may be useful as part of a diagnostic panel, and the identified proteins provide new insights into the pathological mechanisms underlying RMPP.