Study on emm genotyping and drug-resistance of group A Streptococcus pyogens isolated from children in Chaoyang, Beijing,2011

Objective To understand the genotypes of emm gene and the drug-resistance of group A Streptococcus pyogens (GAS) in Chaoyang district, Beijing. Methods Seventy one GAS strains were isolated from the throat swabs taken from hospitalized children. Polymerase chain reaction (PCR) was conducted to amplify and emm gene and the erythrocin resistance related genes: mefA, ermA, ermB and Tn916 gene. The strains' drug susceptibilities to erythromycin and clindamycin were detected with E-test. Results The GAS strains with emm12.0 gene accounted for the highest proportion (87.4%), followed by the strains with emm1.0 gene (9.8%), the strains with emm22.0 gene (1.4%) and strains with emm75.0 gene (1.4%). All of the GAS strains were erythromycin resistant, 95.8% were clindamycin resistant and 95.8% were cross resistant to both antibiotics. The carriage rates of ermA, ermB, mefA and Tn916 genes were 5.6%, 90.1%, 4.2% and 90.1% respectively. Conclusion The most common genotype of GAS strains isolated from the sick children in Chaoyang was emm12.0. The drug resistant rates to erythromycin and clindamycin were high. The ermB gene was the most important erythromycin resistance determinant, while the Tn916 gene was the important determinant of the drug resistance spread in GAS.