| Objective: Group A Streptococcus pyogenes(group A Streptococcus,GAS)is a common gram-positive pathogen,can cause superficial tissue infection,invasive infections and even can cause immune system diseases,or death.At present,in developing and developed countries,the morbidity of GAS infection is renewed.With the discovery of antibiotics,the mortality rate of GAS infection was decreased,but the resistance rate is increasing.Now not only for one drug resistance,but also or a category of drugs,even the same strain was resistant to several kinds of drugs.Therefore,the preparation of effective vaccine is an effective measure to cure GAS infection;however,there are many types of GAS,and the uneven distribution of emm type in different regions,and there have been no reports of the epidemiological investigation of GAS in the northern area of our country for nearly a decade.In this study,the throat swab specimens of healthy children in parts region of Hebei province were screened and the carriage rate of GAS was detected,and the prevalence of GAS infection was analyzed compared with GAS-infected children;at the same time,the resistance to these GAS positive strains was evaluated;finally,the emm genotypes of these GAS positive strains were detected,which were compared with the emm types distribution in China.The purpose of this study is to provide supplementary data for emm gene database of GAS strains in China and provide the theoretical basis for the development of effective GAS vaccine in the northern area.Methods:1 According to《bergey’s manual determinative》and《Clinical microbio-logy examination》,the collected specimens were preliminary determined GAS positive strains,including colony characteristics,gram staining,catalase test and peptide test.2 Suspicious strains were isolated and purified,including purification of blood agar plate and THY liquid shocking culture.3 Bacterial biochemical reaction and drug sensitivity test of GAS was performed by using bacterial plate 96-STREP of zhuhai Deere Company.4 The GAS positive strains were amplified by using the synthesized primers and then purified,which was sequenced by a biological company.5 The sequences of DNA nucleotide were blasted on NCBI,and the emm types of GAS were finally determined.Results:1 GAS positive strains were identified as gram-positive Streptococcus,β-hemolytic ring,catalase testthe negative and bacitracin test positive.2 The carriage rate of GAS in healthy children ranged from 0.86 to 1.84,with an average of 1.55%.3 Healthy children carrying GAS resistance to erythromycin,clindamycin,tetracycline resistance rates were 57.14%,42.86%,28.57%,respectively.4 The prevalence of GAS infection in sick children: resistance rates to erythromycin,clindamycin,tetracycline were 83.33%,75% and 66.67% respectively.5 Emm genotypes in healthy children with GAS were emm12,emm1,emm49,emm23,and the number of bacterial strains were 4 strains,1 strain,1 strain,and 1 strain respecively,emm12 type accounted for the main genotype,the ratio was 57.14%.6 Emm gnotypes of GAS in sick children were emm12,emm1,emm49,emm23,emmM1,and the number of bacterial strains were 7 strains,2 strain,1 strain,1 strain,1 strain,emm12 and emm1 types accounted for the main genotypes,the ratios were 58.33% and 16.67%.Conclusions:1 GAS positive strains was successfully detected in throat swabs speci-mens of healthy children,and the detection rate was about 1.55%.2 The resistant rate of GAS epidemic strains was very high in parts region area of our province,among them,erythromycin resistance cate could reach 83.33%,additionally,there existed multipie drug resistance,and the cross resistance rate of the three drugs was up to 58.33%.3 The distribution of emm gnotypes with GAS epidemic strains in parts region of our province were basically the same to our coutry,mainly emm12 and emm1,among them emm12 much higher than emm1 in proportions. |
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