Molecular Typing And Resistance Of Group A Streptococcus In Shandong Province,2013-2014

[Background]Group A streptococcus (GAS) is a gram-positive bacteria. When GAS infected people, it can cause a series of GAS diseases vary in degree.In our country, scarlet fever caused by GAS has been the class B infectious disease which stipulated according to "Law of the People’s Republic of China on the Prevention and Treatment of Infections Diseases". Especially in 2011, the incidence of scarlet fever was significantly higher than usual, which received widespread attention from various circles of society. Surveillance on the molecular characteristics of GAS strains is important to the prevention and control of GAS diseases.[Objectives]1. To describe the characteristics of molecular types on GAS of Shandong Province in 2013-2014, and to clear the changes and trends of GAS strains in Shandong Province.2. To explore the relationship between emm typing and superantigen genes.3. To compare the advantages and disadvantages of each typing method, and to provide reference for rational selection of typing method.4. To investigate the characteristics of antibiotic resistance, the resistance phenotypes and genotypes on GAS of Shandong Province in 2013, in order to provide reference for clinical treatment of GAS diseases.[Methods]1. The 154 strains of GAS were isolated from throat swabs of children with scarlet fever, pharyngitis, or asymptomatic carriers. It was typed with the methods of emm typing, superantigen genes (speA, speB, speC, speG, speH, spel, speJ, speK, speL, speM, ssa, smeZ) detections, and pulsed-field gel electrophoreses (PFGE).2. The resistance of GAS strains was measured by K-B disk-diffusion method with 8 antibiotics (penicillin, erythromycin, clindamycin, levofloxacin, tetracycline, chloramphenicol, vancomycin, cefotaxime). Positive rates of resistance genes(ermA, ermB, mefA, tetM, tetO) were detected by capillary electrophoresis. The resistance phenotypes were detected by the double dilution method.3. The data was collected and sorted out by Excel 2013, and then analysed by SPSS 19.0. Compared the anvantages and disadvantages of three typing methods of emm typing, superantigen gene profiles, and PFGE by Simpson’s diversity index and Adjusted Wallace coefficients (AW coefficients).[Results]1.5 emm types were detected in Shandong Province,2013-2014. Among them, emm 1 (43.51%) and emm 12 (54.55%) were the dominant types.18 emm subtypes were detected, of which emm1.0 (34.72%) and emm12.0 (45.83%) were the dominant subtypes.2. The positive rate of speA, speB, speC, speG, speH, spel, speJ, speK, speL, speM, smeZ, ssa were 42.21%,100.00%,97.40%,98.70%,32.47%,51.95%,40.91%,0.00%, 0.65%,0.65%,99.35% and 98.70% respectively。3.18 superantigen gene profiles were detected, of which profilel (28.57%), profile2 (32.47%) and profile3 (18.18%) were the most common.4. Both speA and speJ genes were detected primarily in emm 1.0 strains, while speH and spel genes were not detected in emm1.0 strains (P<0.05). And emm12.0 strains were inclined to harbor speH and spel, but not speA or speJ (P<0.05).5.47 different genotypes were identified by PFGE, of which PFGE 16 (23.38%) and PFGE28 (12.99%) were the dominant PFGE genotypes.6. The Simpson’s diversity index of emm types, superantigen gene profiles, PFGE (sma I) were 0.648,0.779 and 0.916 respectively. The concordances were relatively low, AW PFGE(smal)→emm types was the highest (0.707).7. The resistance rates of penicillin, erythromycin, clindamycin, levofloxacin, tetracycline, chloramphenicol, vancomycin, cefotaxime were as follows:0.00%. 100.00%、100.00%、0.00%、92.21%、0.00%、0.00%、0.00%。Two resistance genes of ermB and tetM were detected (both 100.00%). ermA, mefA, tetO were not detected (0.00%). Only one resistance phenotype was detected:cMLS phenotype was found from all the isolated (100.00%). iMLS and M phenotype were not detected(0.00%).[Conclusions]1. Emm types of GAS in Shandong province 2013-2014 mainly focused on emm1.0 and emm12.0. In addition to speK, speL, speM, the positive rate of other superantigen genes was high. Superantigen gene profiles mainly focus on profile 1,2, 3. PFGE 16 and PFGE 18 was the dominant PFGE genotypes.The resistance patterns of GAS was multiple antibiotic resistance of erythromycin-clindamycin-tetracycline.2. There was a correlation between emm types and Superantigen genes.3. Among emm types, superantigen gene profiles, PFGE, the resolving power of PFGE is the highest. The concordances between every type were low, and everyone have advantages and disadvantages, so recommended for using together.