[Study on the super-antigen genes of group A Streptococcus pyogenes strains isolated from patients with scarlet fever and pharyngeal infection, in Beijing, 2015-2017].

Objective: To analyze the characteristics of super-antigen (SAg) of group A Streptococcus pyogenes (GAS), isolated from patients with scarlet fever or pharyngeal infections in Beijing between 2015-2017. Methods: Throat swab specimens from patients with scarlet fever or pharyngeal infections were collected and tested for GAS. Eleven currently known SAg genes including Spe A , spe C , spe G , spe H , spe I , spe J, spe K , spe L , spe M , sme Z and ssa were tested by real-time PCR while M protein genes ( emm genes) were amplified and sequenced by PCR. Results: A total of 377 GAS were isolated from 6 801 throat swab specimens, with the positive rate as 5.5%. There were obvious changes noticed among spe C, spe G, spe H and spe K in three years. A total of 45 SAg genes profiles were observed, according to the SAgs inclusion. There were significant differences appeared in the frequencies among two of the highest SAg genes profiles between emm 1 and emm 12 strains ( χ (2)=38.196, P <0.001; χ (2)=72.310, P <0.001). There also appeared significant differences in the frequencies of spe A, spe H, spe I and spe J between emm 1 and emm 12 strains ( χ (2)=146.154, P <0.001; χ (2)=52.31, P <0.001; χ (2)=58.43, P <0.001; χ (2)=144.70, P <0.001). Conclusions: Obvious changes were noticed among SAg genes including spe C, spe G, spe H and spe K from patients with scarlet fever or pharyngeal infections in Beijing between 2015-2017. SAg genes including spe A, spe H, spe I and spe J appeared to be associated with the emm 1 and emm 12 strains. More kinds of SAg genes profiles were isolated form GAS but with no significant differences seen in the main SAg genes profiles, during the epidemic period.