Study on the relationship between M protein gene-types and superantigen genes of Group A Streptococcus pyogenes strains isolated from scarlet fever patients in Beijing

Abstract

Objective To explore the relationship between superantigen and M protein gene (emm)-types genes of Group A Streptococcus pyogenes (GAS) isolated from patients with scarlet fever in Beijing from May 2012 to July 2013. Methods GAS was isolated from specimens of patients with scarlet fever. Superantigen genes (speA, speB, speC, speF, speG, speH, speI, speJ, speL, speK, speM, ssa, and smeZ), and emm gene were amplified by polymerase chain reaction. Rate and proportion were compared by chi-square test. Results Of the 423 GAS strains isolated from patients with scarlet fever from 2012 to 2013, most of the isolates possessed speB (97.6%), speC (99.8%), speF (98.3%), speG (99.8%), smeZ (94.1%) and ssa (88.4%), and some of them possessed speH (54.6%), speI (53.4%), speA (45.2%) and speJ (43.5%), but very few isolates possessed speK(2.4%), speL(1.4%) and speM(1.7%). Type emm12 (59.5%) and type emm1 (37.4%) were the main types of GAS. Most of the emm12-type isolates possessed speH (84.8%) and speI (84.0%) compared with only 4.0% of speH and 3.4% of speI in type emm1. Most of type emm1 possessed speA (95.3%) and speJ gene (94.6%) compared with only 17.3% of speA and 14.8% of speJ in type emm12. The superantigen genes profiles were significant different between emm 1-type and emm 12-type isolates (P<0.05). Conclusion Type emm1 and type emm12 are epidemic strains in patients with scarlet fever from 2012 to 2013 in Beijing, and emm gene-types are associated with superantigen genes profiles. Key words: Scarlet fever; Streptococcus pyogenes; emm gene; Superantigens