Prevalence of Mycoplasma pneumoniae infection in children in Hengyang and comparison of three methods for genotyping
Objective 
To investigate the prevalence of Mycoplasma pneumoniae (Mp) infection in children in Hengyang from 2013 to 2016 and to analyze the p1 genotypes of the isolated Mp strains by using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), nested polymerase chain reaction (nPCR) and rapid-cycle polymerase chain reaction (Rapid-Cycle PCR). 
 
 
Methods 
Throat swab samples of children with acute respiratory tract infection were collected from four hospitals in Hengyang, Hunan Province from 2013 to 2016. Mp strains in these samples were identified by PCR amplification of the 16S rRNA gene. PCR-RFLP, nPCR and Rapid-Cycle PCR were performed for Mp p1 genotyping in order to further analyze the genotypes of Mp strains circulating in Hengyang. 
 
 
Results 
A total of 109 clinical strains of Mp were identified from the 984 throat swab samples. The sensitivities of PCR-RFLP and nPCR for genotyping MP strains were both 100%, while that of rapid-Cycle PCR was 98.17%. All of the three methods showed 100% specificity for genotyping. Of all isolated Mp strains, 78.90% were p1 gene type Ⅰ and 21.10% were p1 gene type Ⅱ (t=93.239, P=0.01). From 2013 to 2016, the annual isolation rates of p1 gene type Ⅰ and type Ⅱ strains were 93.10%, 87.5%, 76.92%, 65.79% and 6.90%, 12.5%, 23.08%, 34.21%, respectively. The rate of Mp p1 gene type Ⅰ infection decreased over year, while that of p1 gene type Ⅱ infection increased gradually. 
 
 
Conclusion 
PCR-RFLP, nPCR and rapid-Cycle PCR are reliable for genotyping of Mp p1 gene. The predominant genotype of Mp strains circulating in Hengyang is p1 gene type Ⅰ, but the incidence of p1 gene type Ⅱ infection gradually increases from 2013 to 2016. 
 
 
Key words: 
Mycoplasma pneumoniae; p1 gene; Genotype