OBJECTIVEThe P1 protein of Mycoplasma pneumoniae (MP) plays an important role in the pathogenesis of MP pneumonia. It mediates the attachment of the pathogen to host cells and elicits a strong humoral immune response during infection. In early studies, only two types of MP P1 genes were assumed to exist. Later, eight subtypes of MP P1 genes and some variations of P1 gene were reported. However, there are no related reports in China until now. This study aimed to understand epidemiology of MP subtype in Zhejiang province, China, as well as the relationship between MP subtype and clinical severity of MP pneumonia.

METHODClinical samples were collected by nasopharyngeal aspiration from children with MP pneumonia hospitalized in the Children's Hospital of Zhejiang University School of Medicine from February to December in 2009. P1 gene fragment was amplified by using PCR method (with primers of ADH1/ADH2 and ADH3/ADH4, respectively). Then ADH1/ADH2-generated fragments were digested with HaeIII, HpaII, Sau3A, and the ADH3/ADH4-generated fragments digested with HaeIII, Sau3A, HhaI, RsaI. The MP P1 subtypes were determined based on resulting fragments. Part of samples were selected for sequencing. The clinical data of different MP subtype pneumonia were compared.

RESULTA total of 300 hospitalized children with MP pneumonia were enrolled in this study. All the samples produced specific bands for MP P1 gene after PCR with primers of ADH1/ADH2 and ADH3/ADH4 respectively. By restrictive fragment length polymorphism analysis, 297 clinical specimens showed the characteristic band patterns for P1 type 1 identical to Mp129, and only 3 clinical specimens showed the characteristic band pattern for P1 type 2 identical to MP-FH. All P1 type 1 and P1 type 2 showed the same subtype bands respectively, as subtype 1b and 2a. After sequencing, one synonymous point mutation in P1 type 1 was identified relative to the MP129 P1 sequence at nucleotide position (nt) 208(G→A). Three cases with P1 type 2 MP pneumonia were found to have liver damage, and longer hospital stay and fever duration than P1 type 1, but no statistically significant difference was found.

CONCLUSIONClinical samples can be used directly for genotyping of MP. The dominating type of MP in Zhejiang Province was P1 type 1 subtype 1b. But whether there was any relationship between MP subtype and clinical severity remains to be clarified.