Molecular biological characteristics of Streptococcus pyogenes causing children tonsillitis in Yangfangdian community Haidian District of Beijing from 2011 to 2013

Abstract

Objective To analyze the molecular biological characteristics of Streptococcus pyogenes (GAS) causing children tonsillitis in Yangfangdian community Haidian district, Beijing between 2011 and 2013. Methods From Apr.2011 to Apr.2013, there were 94 children with tonsillitis treated in outpatient of Beijing Shijitan Hospital Affiliated to Capital Medical University, and 17 strains GAS were isolated from these pediatrician outpatients.Their encoding mature M protein gene (emm gene), 7 pairs of alleles housekeeping gene (gki, gtr, murI, mutS, recP, xpt and yqiL), superantigen speA and speC genes, macrolide-resistance genes ermB, mefA and ermRT were amplified by polyme-rase chain reaction (PCR). The PCR amplified products of emm gene and 7 pairs of alleles housekeeping gene were sequenced.The emm gene sequences were stored in the Centers for Disease Control and Prevention database.The emm types of GAS were identified.The 7 pairs of alleles housekeeping gene sequences of GAS were sent to the multilocus sequence typing (MLST) website for their iso-allelic sequences to identify their sequence types (ST). The PCR amplified products of superantigen gene speA and speC, macrolide-resistance genes ermB, mefA and ermRT were performed with agar gel electrophoresis.The corresponding qualitative results were obtained. Results Five emm-types were disco-vered: emm12.0 (76.4%), emm1.0(5.9%), emm89.0(5.9%), emm75.0(5.9%)and emm22.0(5.9%); emm12.0 and its subtype strains had the same allelic profiles which belonged to ST36 type; emm1.0 strain belonged to ST28; emm89.0 strain belonged to ST101; emm75.0 strain belonged to ST49; emm22.0 strain belonged to ST46; 94.1% (16/17) strains carried macrolide-resistance gene ermB.None carried macrolide-resistance genes mefA and ermRT.None carried superantigen speA gene.100.0% (17/17 cases) carried superantigen speC gene. Conclusions emm12.0 (ST36) strain was the most common type of GAS causing the children tonsillitis in Yangfangdian community Haidian District, Beijing between 2011 and 2013.These strains mainly carry macrolide-resistance ermB and superantigen speC gene. Key words: Tonsillitis; Streptococcus pyogenes; Child