研究在儿童社区获得性急性下呼吸道感染（acute lower respiratory tract infection，ALRTI）中肺炎支原体（Mycoplasma pneumoniae，MP）和沙眼衣原体（Chlamydia trachomatis，CT）的感染特征。采用实时荧光定量聚合酶链反应（real-time PCR）检测2006年10月至2008年2月期间，因ALRTI住复旦大学儿科医院的儿童呼吸道标本中MP和CT 的DNA，并分析两种病原体感染儿童的临床特征与实验室结果。在1312份深部鼻咽分泌物标本中，MP和CT实时荧光定量PCR检出率分别为7.85% (103/1312)和2.97% (39/1312)，MP在5岁以上儿童中的检出率为33.33%(30/90)，而CT在3月以下儿童中的检出率为6.28%(31/494)。MP感染后更易有40℃以上的高热表现，但较少有发绀与重症呼吸道感染的表现，白细胞计数常无明显的升高，但C反应蛋白升高较多见；CT感染后40℃以上的高热和重症呼吸道感染少见，C反应蛋白升高较少见。研究发现，在5岁以上儿童社区获得性ALRTI中，MP是重要的病原体，而在3月以下儿童中，CT为常见病原体之一。

To investigate the characteristics of mycoplasma pneumonia(MP) and chlamydia trachomatis(CT) in hospitalized children with acute lower respiratory tract infection in Shanghai area. From Oct 2006 to Feb 2008, 1312 sputum samples from 1312 cases of acute low respiratory tract infection who were hospitalized in our hospital in Shanghai were collected and tested by real-time PCR for MP and CT DNA. Clinical characteristics and basic laboratory examinations of the positive cases were analyzed. The detection rates of MP were 7.85% (103/1312) and CT were 2.97% (39/1312), respectively. MP was identified most commonly in children > 5 years old with a detection rate of 34.5%. CT was mainly detected in infants < 3 months of age with a detection rate of 6.8%. MP infected cases seems to have more chances of high fever, but rare cyanosis or severe respiratory tract infections. Their peripheral white blood cell count was always in the normal range, but CRP was elevated. CT infected cases seldom have high fever or severe respiratory tract infections，their CRP always in the normal range. From our study, we confirm that MP is a significant cause of ALRTI in children younger than 5 years old. CT plays an important role in infants younger than 3 months old due to ALRTI.