| Background: Chlamydia pneumoniae is an intracellular pathogen that has been suggested to play a role in the pathology of respiratory system diseases, especially asthma. However, so far none of the studies have provided clear evidence for a causative role of CP infections in asthma. The former seroepidemiologic investigations showed that CP is a common cause of respiratory tract infection in children between 5 and 15 and the clinical symptoms are mild or asymptomatic. There were a few studies reported about CP infection in children under 5-year of age. The importance of Chlamydia pneumoniae respiratory tract infection with multi-assay in childhood is under discussion.Objective: To investigate the distribution of children ages and seasons of CP infection in Soochow and compare Quant-ELISA with PCR (nest-PCR or fluorescent quantitation-PCR) in sensibility, specificity and correlation. In addition, discussing the correlation between CP infection of respiratory tract and wheezing, allergen sensitization or asthma was also included. Meanwhile, we analyzed specific antibodies in parents'serum to discuss whether there was correlation between parents'infection and children.Measurements: patients with acute respiratory tract infection on admission during 2005.11 to 2006.10 were enrolled and 2ml venous blood was adopted for 1813 patients, and 543 patients provided for paired serum as well as 153 parents'serum. Both CP IgG and IgA were detected by quant ELISA for diagnosis of acute infection. In the meanwhile, sputum which were detected by nest-PCR or FQ-PCR were adopted in 1508 patients within 24 hours. 1358 patients'sputum were taken for bacterial culture and several common viruses were detected by using direct fluorescence assay (DFA). A part of patients with wheezing including patients with asthma screened air and food allergen. Results: 207/1813 of patients accorded with standard for acute infection. PCR and ELISA positive were 6.56% and 6.45% separately, and 14.28% together. There was a poor correlation between such two methods. Single serum and paired serum existed significant difference (p<0.05). according to age distribution, no difference was found by PCR, but sero-positive was lower at age of 1 to 3 years old, then up to 9.20% (24/2641) at age 4 to 6 years old, and at the age of≥7 years old the positive climbed to 15.13% (18/119). As can be seen, the sero-positive increased with the age growing. According to different seasons, there was no different among all seasons, compared to PCR, sero-positive was higher in winter (p<0.05). When it comes to different diseases, positive in acut bronchitis was 11.17% (p<0.05) as well as higher positive of lobar pneumonia and sinusitis, 15.91% and 16.67% separately. Combined infection rate accounted for 59.28% in all patient infected by CP. There was a strong association between CP and RSV infection. Otherwise, cross infection among children and their parents was common in our study. There existed linear correlation between children IgG antibodies and their mothers and no correlation was found with IgA antibodies. The clinical manifestation of CP infection was milder than MP infection with shorter course of disease and holiday days (p<0.05). In patients with low respiratory tract infection, RSV and CP infection frequently caused wheezing than no pathogen patients. There was no significant different between wheezing and allergen sensitizations. Besides, no significance of positive detecting by PCR was found between non-atopic asthma and atopic asthma.Conclusions: CP infections in children under 3 years of age were not common, then, infection rate climbed with the increasing age. So far, further study should be taken for standardization of detection measurements. There was a poor correlation between PCR and ELISA. To some extent, positive PCR was responsible for early infection. CP infection in winter was more than other seasons and there was a strong correlation between CP infection and RSV infection. Our study also demonstrated that children and their parents existed cross infection. IgG antibodies under 1 year old maybe come from their mothers. The clinical manifestation was mild, maybe, a portion of outpatient did not need to be hospitalized. CP was a common causative pathogen in low respiratory tract infection that resulted in wheezing. Accumulating evidence suggests that CP, an intracellular ubiquitous pathogen with an innate propensity to persist and cause chronic infections, which play a important role in pathopoiesis of asthma. Our study did not provide clear evidence that wheezing caused by CP associated with allergen sensitization. |
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