Emm type,macrolide-resistance genes and superantigen gene profile among GAS isolate from children with pharyngitis in Chongqing

Objective:To analyze emm type,macrolide-resistance genes and superantigen gene profile of GAS isolates from children with pharyngitis in Chongqing.Methods:A total of 44 clinical isolates of GAS were obtained from children with pharyngeal diseases in 2007,Chongqing.The macrolide-resistant genotype(ermB,ermTR and mefA) and superantigen gene of group A streptococcal isolates(ssa、SMEZ、speA、speC、speG、speH、speI and speJ)were detected by PCR.Emm types were applied by PCR and sequencing.Results:Emm12 was the most common emm type(26 isolates,59.1%).Emm1 was the second(7 isolates,15.9%).Emm22 had 2 isolates,emm6 had 2 isolates,emm3 had 2 isolates,and emm80,emm63,emm102,stG485 and st1815 had 1 isolate respectively.All 44 isolates were detected ermB gene(100%),33 isolates were detected erm TR gene(75.0%),and 3 isolates were detected mefA gene(6.8%).All of the isolates were detected ssa,SMEZ and speH.The detection rates of other superantigen genes were speG(84.1%),spec(81.2%),speI(63.6%),speA(50%)and speJ(15.9%).Six in 7 isolates of emm1 type were detected speA gene(85.7%),and 7 in 26 isolates of emm12 type were detected speA gene(26.9%).The distribution of speA in emm1 and emm12 had a statistically significant difference(P=0.008,0.05).The distribution of macrolide-resistant genotypes was at random,and had no correlation with emm types.Conclusion:The most prevalent emm types in pharyngeal isolates in Chongqing were emm12 and emm1.The macrolide-resistant mechanism was mostly determined by the change of target site in the 23SrRNA methylase encoded by erythromycin resistance methylase B(ermB) genes.Emm type was not apparantly related to macrolide-resistance genes,and the distribution of speA was mainly related to emml.