Clinical Characteristics And Mechanism Research Of Refractory Mycoplasma Pneumoniae Pneumonia In Children

Objective: To seek the early discriminant of clinical manifestations and intervention measures of refractory Mycoplasma Pneumoniae Pneumonia(RMPP) in children. To study the status quo of drug-resistant genes of Mycoplasma Pneumoniae in Suzhou, and the relationship between MP 23 S r RNA gene mutation and RMPP. To explore the expressed level, clinical significance of s B7-H3 in the bronchoalveolar lavage fluid(BALF) of RMPP in children and the relationship between s B7-H3 and various cytokines.Methods: Sixty-three cases of hospitalized children with RMPP(RMPP group) were collected from October 2013 to September 2014 in Children’s Hospital Affiliated to Soochow University. Thirty-two cases of hospitalized children with Mycoplasma Pneumoniae Pneumonia(MPP group) were collected as control group in the same period. Clinical datas of children were collected for comparative analysis. The bronchoalveolar lavage fluids(BALF)/nasopharyngeal aspirates(NPA) of forty-eight hospitalized children with RMPP(RMPP group) and thirty-two hospitalized children with MPP(MPP group) were collected in the same period. We amplified prone to mutation gene segment of 23 S r RNA V areas of MP with PCR and sequence the amplification of product. We compared the results with the gene sequence of MP standard strains(MP129). In the same period the BALF of forty-three hospitalized children with RMPP(RMPP group) were collected for the diagnosis and treatment and in which thirty cases had collected the BALF for the second time. The BALF of fifteen hospitalized children with bronchial foreign body were collected as control group. The expression levels of s B7-H3, IFN-γ, TNF-α, GM-CSF, IL-1β and IL-8 in the BALF were detected by enzyme-linked immunosorbent assay(ELISA). The expression levels of s B7-H3, IFN-γ, TNF-α, GM-CSF, IL-1β and IL-8 in the BALF at the acute phase were compared with control group and the group after treatment. The expression levels of s B7-H3, IFN-γ, TNF-α, GM-CSF, IL-1β and IL-8 in the BALF after treatment were compared with control group. We analyzed the correlation between the level of s B7-H3 and IFN-γ, TNF-α, GM-CSF, IL-1β, IL-8 in the BALF of RMPP children at acute stage.Results: The average age of RMPP group was higher than that of MPP group. The average fever period of RMPP group(16.17±4.60 days) was higher than that of MPP group(6.97±1.77 days). The incidence of lobar pneumonia, decreased breath sounds and lung percussion dullness in RMPP group were higher than those in MPP group. The MP DNA copies in the BALF of RMPP were higher than that of MPP group. Total WBC count, neutrophil percentage, LDH, Ig G, Ig A and Ig M in the peripheral blood of RMPP group were higher than those of MPP group. The incidence of CRP > 40 mg/L and elevated ALT of RMPP group were higher than those of MPP group. The incidence of pleural effusion and liver damage of RMPP group were higher than those of MPP group. The cases of washing by bronchoscope, the antifebrile time after treatment of macrolide antibiotics and hospitalization days of RMPP group were significantly higher than those of MPP group.In forty-eight RMPP cases, forty-six cases gene sequence had gene point mutations of the amplification product of 23 S r RNA gene with MP PCR in RMPP group. The percentage of gene point mutations was 95.8%. They were all A to G mutation at position 2063. Twenty-eight cases gene sequence had gene point mutations of the amplification product of 23 S r RNA gene with MP PCR in MPP group, and the percentage of gene point mutations was 87.5%. All mutations were A to G mutation at position 2063. There was no significance between the two groups. Seventy-four cases had gene point mutations of 23 S r RNA gene in RMPP group and MPP group, and the percentage of gene point mutations was 92.5%(74/80). All of them were A to G mutation at position 2063.The levels of s B7-H3, IFN-γ, TNF-α, GM-CSF, IL-1β and IL-8 in the BALF at acute stage of RMPP group in children were higher than that of the group after treatment and the control group. The levels of s B7-H3, TNF-α, IFN-γ in the BALF of RMPP after treatment were higher than those in control group. The levels of GM-CSF、IL-1β、IL-8 in the BALF of RMPP after treatment and control group had no significant difference. The levels of s B7-H3 had positive correlation with the levels of IL-1β、GM-CSF, and the level of s B7-H3 had no correlation with the levels of IL-8、TNF-α、IFN-γ.Conculsion:(1) RMPP is more likely to the elder children, appearing lobar lung inflammation, high MP DNA copies in BALF, long thermal process, high incidence of liver damage, high incidence of washing treatment by bronchoscopy and long hospitalization days.(2) The condition of drug-resistance of Mycoplasma Pneumoniae in Sochow area is at high level, and the percentage of gene point mutations is 92.5%. All of them are A to G mutation at the position 2063 of MP 23 S r RNA genes.(3) MP drug resistance has no significant correlation with the severity of illness, and MP drug resistance may not be the main factor of the emergence of RMPP.(4) s B7-H3 may control mononuclear macrophage to produce inflammation factor, and participate in the immune response and lung injury after MP infection, which may lead to occurrence and development of RMPP.