Detection Of Mycoplasma Pneumoniae For Respiratory Tract Infection In Children And Typing Of Xi'an Strains

Mycoplasma pneumoniae(MP) is a causative agent of tracheobronchitis and primary atypical pneumonia among children and one of the most common causes for community-acquired pneumonia(CAP) among adults. It causes diseases via direct injury and immune mechanisms. MP causes not only acute respiratory diseases ranging from severity from mild to life-threatening, but also extra pulmonary complications and infections, involving the heart, central nervous system, and urinary system.Infection of MP has occurred around the world. According to report Domestic and abroad, the morbidity rates of MP ranges from 0.6% to 47%. Nelson Essentials of Pediatrics also suggests that MP accounts for 70% of children's community-acquired pneumonia. Meanwhile, other resources also indicate that MP has certain epidemic and non-epidemic years, as well as age distribution and seasonal peak, etc.Previously, the infection of MP can be provisionally diagnosed only by Non-specific symptoms, such as chest radiographic abnormalities, cough, fever, white blood cell (WBC) counts, and C-reactive protein (CRP). With the development of laboratory diagnostic techniques, the Etiological diagnosis of MP can be achieved by cultivation, serological methods and polymerase chain reaction (PCR) et al. In early diagnosis of MP, serological methods and PCR are more effective. In recent years, MP rapid liquid culture is widely used clinically.In the experiment, MP rapid liquid culture, rapid liquid culture combined with microscopy, ELISA, nPCR and real-time PCR are used to examine MP in the specimens, and the results are statistically analyzed. Positive specimens of rapid liquid culture are further assayed by the automated microbial identification system to investigate which microorganisms caused the false-positive. In addition, we analyzed MP-IgM detections of Department of Pediatrics, Xijing Hospital in 2002-2009, and typed MP of Xi'an strains recently. The results indicate that:1. Significant difference is detected between the results by rapid liquid culture and those by microscopy, ELISA, nPCR and real-time PCR. Using microscope to examine the positive specimens of rapid liquid culture can effectively reduce the false-positive rate of MP, and the sensitivity is consistent with that on PCR. The ordinary sensitive bacteria can be inhibited effectively in MP rapid liquid culture medium. Fungi and drug-resistant strains are the main causes of the false-positive on MP rapid liquid culture. However, such false-positive cannot be identified and excluded on microscopy.2. During 2002-2009, there were 3 MP outbreaks in Xi'an, and the Epidemic peaked every 3 years at least. MP has clear epidemic seasons. The peak of MP infection is in autumn and winter every year. There is significant difference of MP-IgM positive rate between epidemic and non-epidemic season, and between epidemic and non-epidemic years. MP-IgM positive rate was significantly different in all age group. In 0 ~1 years old group, MP-IgM positive rate was the lowest; in 6~9 years old group, the rate was the highest.3. The recent epidemic genotype of MP Xi'an strains is P1-â… type.