| Streptococcus suis(SS) is an important pathogen of human and animal.Thirty-five capsular serotype of Streptococcus suis have been described(tyupesl/2 and 1 through 34).first of all, Serotype 2(SS2) is considered to be the most-virulent serotype and prevalent in worldwide, then is Serotype 1(SS1), Serotype 7(SS7), Serotype 9(SS9).is prevalent in Germany, Belgium, Spain, Holland, while SS7 is prevalent in Finland. In China, Guangdong province firstly isolated SS2 in 1991, later, human Streptococcus suis infection in Jiangsu province and Sichuan province happened in 1998 and 2005,respectively.Shanghai is one of the most sweeping swine breeding aquatics, export and import in China, therefore, it is necessary to investigate the circs of the Streptococcus suis and its virulent factors, in order to prevent and control breaking out the Streptococcus suis in Shanghai in future.Our research process the investigation of 6 primary serotype and 7 virulent factors of streptococcus suis in Shanghai, based on daily clinic samples in Shanghai Municipal Animal Husbandry and Veterinary Station and swine nose samples in 2005 to 2007.Firstly of all, isolating the swine Streptococcus from the samples, 306 isolates of swine Streptococcus had been obtained in Shanghai area during the year of 2005 to 2007.The morphological cultural characters indicated that the isolated bacteria belonged to genus streptococcus.Furthermore, 306 isolates were detected by Lancefild group A-G latex diagnostic kit and by PCR with 16S rRNA and gdh. The results stated that groupe C(40.7%) is primary, the next is Streptococcus suis(13.1%),group A is 1.9%,group B is 7.4%,group E is 6.5%,and some isolate were not belonged to group A-G,(22%).Then, the method of PCR for detecting different serotypes (1, 1/2, 2, 7, 9 and 14 )of streptococcus suis based on PCR technique, which was developed to amplify the four specific gene fragment of CPS1I, CPS2J, CPS7H and CPS9H. 32 isolates has been detected by using above PCR method, the result of detection is (3 SS1, 8 SS2, 2 SS7 and 2 SS9),the rest are not belong to above 6 serotypes. The result of detection is the same to sequencing result. Compared the positive sequent with the sequent published in genebank, all of them are very similar.At last, the method of two separate multiplex PCR for detecting seven virulence-associated factors based on the gene sequences of mrp(the muramidase-released protein gene).epf(the extracellular factor gene).sly(the suilysin gene).gdh(the glutamate dehydrogenase gene).gapdh(the fibronectin-binding protein gene),orf2 and fbps.which was developed by combining and optimizing the seven virulence-associated factors.32 isolates were detected by the multiplex assay. All the PCR products were detected by electrophoresis on 2% agarose gels. The results of the detection of 32 Streptococcus suis were confirmed by the bacteriological examination. Both the positive control and negative control were successful. The results demonstrated that multiplex PCR was highly specific and sensitive diagnostic tool for the detection of seven virulence-associated factors of Streptococcus suis.In order to know more about the 4 serotypes and discuss the relationship between the virulent factors and the isolate virulence, the rabbit and Zebrafish animal model had been developed. The results indicated that 4 serotype of Streptococcus suis, SS2 is the most virulent to rabbits and Zebrafish,while SS1,SS7,SS9 were not sensitive to rabbits and Zebrafish. As the result, the virulence of the Streptococcus suis isolates has some relationship with virulent factors of Streptococcus suis. |
