A Preliminary Study On The Pathogenesis Of Mycoplasma Pneumoniae Pneumonia And The Manifestation Outside The Lung

Mycoplasma pneumoniae is a kind of pathogenic microorganism which is a common pathogen of children's respiratory tract infections. Recently years, the number of MPP is increasing and it may complicate multisystem injury. But the pathogenesy hasn't been unitive.This research. study the pathogenesis of mycoplasma pneumoniae pneumonia and the manifestation outside the lung preliminarily via animal experiments and clinical investigation.The details is as below:1. Animal experiment:1.1 MPP mice modelDivide the ICR mice into 3 groups randomly (low dose infection group, high dose infection group, and normal control group). The MPP model is made by inoculating MP intranasally for 2 days and judged with lung pathological score and PCR of lung homogenate .The model's achievement ratio is respectively 50% and 100% in low dose infection group and high dose infection group.SlightInflammation occures on the 1st day , most severe on the 4th day and recover on the 8th day after infection.1.2 White cell count and MP-DNA-PCR of BALFCollect mice's BALF and count the number of leukocytes. The result is that on the 1st and the 4th day, the high dose infection group is significant higher than the normal control group(P<0.05),and there is no significant difference between low dose infection group and the normal control group, and on the 8th day there is no different between the 3 groups. On the 1st day, the PCR of the 2 infection groups are both positive(50%,100%) .On the 4th day only the high dose infection group is positive(16.7%),and on the 8th day all the 3 groups are negative. So MPP may be correlated with the MP direct invade.1.3 Lymphocyte transformation of mice's spleenWe use MTT colorimetric method to carry out this test. The result shows that on the 4th day and 8th day after the infection, there're significant differences between high dose infection group and the other two groups(P<0.05).The results prove that MP infection make T lymphocytes of mice's spleen proliferate.A high infective dose can make the proliferation more manifest and can have a longer duration.1.4 Observation of the manifestation outside the lung Observe the clinical situation of the mice in each group. iIt shows that on the 4th day after the infection, when compare the high dose group with the other two groups, the mice grow slower(P<0.05). However, there're no significant difference between the low dose infection group and normal control group(P>0.05). On the 8th day the high dose group grows significant slower than the other two groups(P<0.05, P<0.01).But not significant between the low dose infection group and normal control group(P>0.05). The result hints that MP infection may impact the growth of the mice .There are no pathological changes of brain, liver, heart and kidney in low dose infection group and there are 3 mice have manifestations outside the lung.But the homogenate MP–DNA-PCR are negative corresponding which illustrate that immunologic mechanism may participate the mainly manifestations outside the lung.The serum CIC test shows that on the 4th day after the infection, the high dose group is significant higher than the other two groups(P<0.05). However, there're no significant difference between the low dose infection group and normal control group(P>0.05). On the 8th day the CIC of high dose group is significant higher than the other two group(sP<0.05, P<0.01).But not significant between the low dose infection group and normal control group(P>0.05).The results prove that MP infection make serum CIC rise.A high infective dose can make the rise more manifest and can have a longer duration.So CIC may participate the mainly manifestations outside the lung.2.Clinical observationsSelect 49 MP infection children according to the MP infection diagnosis standard, 27 (55.1%) male and 22(44.9%) female, male female ratio is 1.23:1; the age is from 3 month to 14 years old and 4.3 years old for everage; there're 8 infants (16.3%), 12 young children (24.5%), 17 preschoolage children (34.7%) and 12 schoolage children (24.5%). According to the clinical manifestations and auxiliary examination add up MPP and the manifestations outside the lung. The result is that there are totally 35 simple MP pneumonia (74.1%) and 14 the manifestations outside the lung (28.6%) in which there're 3 myocarditis (6.1%), 2 proteinuria (4.1%), 2 anaphylactoid purpura (4.1%), 3 liver functional lesion (6.1%) and 4 hematological damage (8.2%),3 is thrombocytosis and 1 is granulocytopenia.Collect serum at acute and recovery stage,choose simple MPP and MPP with manifestations outside the lung randomly,6 each. The serum CIC test shows that the difference between acute stage and control group is significant(P<0.05),but the difference between recovery stage and acute stage is not significant ,either between recovery stage and control group(P>0.05).that is CIC rising significant in acute stage. In acute stage CIC between simple MPP and MPP with manifestations outside the lung is significant(P<0.05),but in recovery stage the difference is not significant(P>0.05).the result hints that CIC may participate in the immune mechanism of MPP's the manifestation outside the lung. So MP infection may cause the cell and humoral immune functional disorder.The occurance of MPP is not only related with the direct invasion of the pathogen but its manifestation outside the lung is also related intimately with cell immunity as well as humoral immunity.