Correlation Between The Bacterial Load In Nasopharyngeal Aspirates And Clinical Severity In Children With Mycoplasma Pneumoniae Pneumonia

Objective:Detect Mycoplasma pneumoniae(MP)loads in nasopharyngeal aspirates of children with Mycoplasma pneumoniae pneumonia(MPP)by quantitative polymerase chain reaction(q PCR),and to explore the relationship between MP loads and clinical severity,so as to provide basis for clinical condition evaluation.Methods:The medical records of 400 children with MPP admitted to the Children’s Hospital of Chongqing Medical University from August2010 to December 2016 were retrospectively collected,including the children’s basic personal information,clinical symptoms,laboratory serology,chest x-ray,computed tomography(CT),and ultrasound findings.1)MP-DNA was quantified in nasopharyngeal aspirates by quantitative polymerase chain reaction technique,and according to the detection,the results were artificially divided into five groups:low copy number group(≥10~2 and<10~5copies/ml),low-medium copy number group(≥10~5 and<10~6copies/ml),medium copy number group(≥10~6 and<10~7 copies/ml),medium-high copy number group(≥10~7 and<10~8 copies/ml)and high copy number group(≥10~8 copies/ml).The differences in clinical performance and laboratory serological indices between the groups were compared by chi-square test and analysis of variance;2)Spearman’s correlation coefficient and grey relational model were used to study the correlation and degree of association between MP loads and each variables.Results:1)The data of this group showed that the proportion of high fever and children of severe or refractory Mycoplasma pneumoniae pneumonia in the high copy number group of MP-DNA(≥10~8 copies/ml)was higher than that in the other four groups,and the difference was statistically significant(P<0.05).While other clinical features such as gender,three depression sign,cyanosis,shortness of breath,wheezing,atelectasis,and pleural effusion had no significant difference among the groups.2)MP loads of children with mycoplasma pneumoniae pneumonia were positively correlated with fever peak,fever duration,days of hospitalization,lactate dehydrogenase(LDH),C-reactive protein(CRP)and negatively correlation with lymphocyte ratio,and the difference was statistically significant(P<0.05).The degree of correlation was:fever peak>lymphocyte ratio>fever duration>days of hospitalization>LDH>CRP.Conclusion:The MP loads of children with Mycoplasma pneumoniae pneumonia is related to the clinical severity.The high bacterial load of Mycoplasma pneumoniae indicates that children are more likely to have high fever,severe or refractory Mycoplasma pneumoniae pneumonia,longer fever duration and hospitalization days,and higher CRP and LDH values,lower lymphocyte ratio.Therefore,the MP loads in nasopharyngeal aspirates measured by q PCR technology are helpful to evaluate the severity of MPP in children.