Etiologic Investigation Of Mycoplasma Pneumoniae In Lower Respiratory Tract Infections In Children

[Background and Objective] Mycoplasma pneumoniae(MP) is one of the main pathogens in respiratory tract infections. MP could cause upper respiratory tract infections as well as lower respiratory tract infections. It can cause damage to many organs by immunologic mechanism, such as encephalitis, myocarditis, hepatitis, nephritis and so on. Some studies indicated that MP had close relationship with asthma,SLE and infectious monocytosis. There are more and more MP infections in the past few years. Mycoplasma pneumoniae is the pathogen of 10%-20% of community acquired pneumonia in children, in certain years 30%. There are more MP infections in winter in the north and more in summer in the south. There are also opposite opinions. MP infections have relationship with age. Most of these studies considered that there were more MP infections in elder children. But recently there were studies about the age of onset becoming younger and younger. Studies about the relationship between MP infection and sex are unconformable. Some studies indicated that there was no relationship. Some studies showed more in male or female. It is easy to diagnose typical MP infection. We usually diagnose atypical MP infection by laboratory assays. There are classic cultivation,serology detection methods and nucleic acid detection methods. Serology methods conclude CF, PA, IHT and ELISA. Nucleic acid detection methods conclude conventional PCR, semi-quantitative PCR, nPCR, real time PCR and so on. PCR and serology detection methods are both used in clinical work.Fever, pharyngodynia and cough are the main clinical symptoms of MP infection. Some could have gasping. There are four kinds of X ray: increased hilar shadow density,bronchopneumonia,interstitial pneumonia and homogeneous consol shadow. These changes can transmigrate. MP can causing lobar pneumonia, pleural effusion, lung abscess ,and lung cyst was also reported in the past few years.In clinical, we usually use macrolides and FQNS to treat MP infection. FQNS can damage joints of small animals,so we often use macrolides in children, such as erythromycin and azithromycin. The density of erythromycin is higher in blood than in tissues. But the density of azithromycin is higher in tissues than in blood.Erythromycin is suggested to use when having fever and MP in blood. Azithromycin is suggested to use when fever disappears. There were some studies concerned with MP septicemia. These studies extracted white blood cells to detect MP nucleic acid. We investigated MP-IgM of 1192 children with lower respiratory tract infections and wanted to find out current situation of MP infection in children with lower respiratory tract infections and validate MP in blood, so that we could make better treatment plans and raise new search directions.[Patients and Methods] From January 2007 to December 2007, 1192 hospitalised children with lower respiratory tract infections were enrolled in this investigation,of them 827 boys and 365 girls aged from 40 days to 14 years.The IgM antibody of MP was evaluated with ELISA. The result which was higher than 1:40 was considered positive. We recorded data of the invasion time, clinical symptoms, blood routine, CRP and X rays of children infected with MP. We randomly chose 25 children with MP pneumonia and evaluated MP DNA by FQ-PCR in blood serum.All the data was evaluated by SPSS10.0. Variance analysis was used to detect the inter-group difference. x2 test was applied to compare counting data. P-value <0.05 was considered significant importance.[Results] MP infection could happen in every season. There was small prevalence from July 2007 to December 2007 in this area. The ratio of MP infection had relationship with age and sex. The ratio of MP infection in female was higher than male. 4~6 yr group and 7~14 yr group were both higher than 0~3 yr group. The ratio of MP infection in 4~6 yr group and 7~14 yr group had no significant difference. The ratio of MP infection was different in different kinds of lower respiratory tract infections. The ratio of MP infection in bronchitis group, pneumonia group and asthma with respiratory tract infections group had no significant difference. Asthma with respiratory tract infection group was higher than pneumonia group. Bronchitis group, pneumonia group and asthma with respiratory tract infection group were all higher than bronchiolitis group. Fever in 7~14 yr group lasted the longest. Other clinical data analysis had no significant difference in the three groups. Big schistic shadow ,pleural effussion were more in 6~14 yr group than 0~5 yr group. Children of the 0~5 yr group appeared more bilateral lung changes than the 6~14 yr group. There were many kinds of complications in MP positive children with lower respiratory tract infections. Myocarditis was common. MP truly existed in blood.[Conclusions] MP might be one of the main pathogens in lower respiratory tract trinfections. MP infection could happen during the year. The incidence of MP infection was higher from July to December. MP infection may be correlated with age and sex. The incidence was higher in pre-school age children and school age children than young children. It was higher in female than male. Fever lasted for a long time in school age children. The incidence of MP infection might be low in bronchiolitis and high in asthma complicated with respiratory tract infections. There were many kinds of X ray. The incidence of large foliated shadow and pleural effusion was higher in children older than five years old. These were more lateral lung changes in these children who were yonger than five years old. There were many kinds of manifestations out of lungs in MP pneumonia. MP truly existed in blood.