Distribution characteristics of emm genotype and superantigen of Group A Streptococcus isolated from the pharynx of children with scarlet fever-like erythema in Beijing / 中华实用儿科临床杂志

ABSTRACT

Objective:To analyze the genetic characteristics of Group A Streptococcus (GAS) isolated from the pharynx of children with scarlet fever-like erythema. Methods:Pharyngeal GAS isolates were collected retrospectively from children with scarlet fever-like erythema admitted in the Department of Dermatology, Beijing Children′s Hospital, Capital Medical University from June 2019 to February 2020.PCR and sequencing were used to detect emm genotyping and superantigen genes( speA, speB, speC, speF, speG, speH, speI, speJ, speK, speL, speM, ssa and smeZ) of the isolates.Data were compared by the chi-square test or Fisher′ s exact test between groups. Results:A total of 147 GAS strains were collected.The main emm genotypes were emm1.0 in 76 strains (51.70%) and emm12.0 in 60 strains (40.82%). Other 7 emm genotypes were all found in less than 5 strains.The detection rate of speF, smeZ, speG, speC, speB and ssa were as high as 100.00%(147/147 strains), 100.00%(147/147 strains), 99.32%(146/147 strains), 95.24%(140/147 strains), 94.56%(139/147 strains) and 92.52%(136/147 strains), respectively. speA, speJ, speI, speH and speM had a low detection rate of 51.70%(76/147 strains), 49.66%(73/147 strains), 32.65%(48/147 strains), 23.81%(35/147 strains) and 4.08%(6/147 strains), respectively.No speK and speL were detected.The frequencies of speA and speJ in emm1.0 strains (65/76 strains, 85.53% and 64/76 strains, 84.21%) were significantly higher than those in emm12.0 strains (4/60 strains, 6.67% and 6/60 strains, 10.00%). However, the frequencies of speH and speI in emm1.0 strains (7/76 strains, 9.21% and 2/76 strains, 2.63%) were significantly lower than those in emm12.0 strains (28/60 strains, 46.67% and 45/60 strains, 75.00%) (all P<0.001). Conclusions:At present, emm1.0 and emm12.0 are the main GAS strains isolated from the throat of children with scarlet fever-like erythema in Beijing, and emm1.0 is more common.There is a correlation between emm genotyping and the superantigen gene profile.Type 1 superantigen gene profile is significantly more frequently detected in emm1.0 strains than in emm12.0 strains.Type 2, 3 and 4 superantigen gene profiles are significantly more frequently detected in emm12.0 strains than in emm1.0 strains.