M protein gene of group A streptococcus isolated from children with pharyngeal infection in Beijing, 2011-2014

Objective To learn about the distribution of M protein gene (emm) of group A streptococcus (GAS) isolated from the children cases of phrayngeal infection in Beijing from 2011 to 2014. Methods The pharyngeal swabs were collected from the children who were diagnosed with pharyngeal infection in pediatric outpatient departments or emergency rooms of 36 hospitals in Beijing from 2011 to 2014. The emm sequencing and subtyping were performed with polymerase chain reaction. The distribution of emm genotypes were analyzed. Results There were 739 cases who met the inclusion criteria of the study. Ten emm types and 32 emm subtypes were detected, in which emm12 and emm1 were the major types, accounting for 62.2% and 35.0% of the total respectively; emm12.00 and emm1.00 were the major subtypes, accounting for 53.2% and 31.9% of the total respectively. Two new subtypes were detected, i.e. st1258 and st485. The cases infected with GAS emm12 mainly lived in the downtown, accounting for 59.8%. The cases infected with GAS emm1 mainly lived in the northern suburb, accounting for 49.4%. The area, time and age specific differences in the distribution of emm12 and emm1 had statistical significance, while the sex specific difference had no statistical significance. Conclusion The predominant emm types of GAS isolated in Beijing from 2011 to 2014 were emm12 and emm1. The area and age specific differences in the distributions of emm12 and emm1 were statistical significant.