Determination On Part Of Virulence Gene Sequence And Investigation On Serology Of Streptococcus Suis Type 2

Streptococcus suis serotype 2 is an important pathogen of zoonosis, which not only causes meningitis, arthritis, endocarditis, blood posioning pneumonia and sudden death in pig, but also infects correlated people and led to death.In recent year, Streptococcus suis serotype 2 sometimes presents epidemic outbreak in our country, which has greatly affected the development of swine industry and social republic hygienic safety. Some problems about the pathogenic biology and epidemiology of Streptococcus suis serotype 2 is still not clear, which lacks essential and enough basis on studying the susceptible level and the risk of interpersonal infection in different areas of Streptococcus suis serotype 2. Therefore, we develop the research on pathogenic diagnosis and serological diagnosis techniques to investigate and analyse the serum antibody level of Streptococcus suis serotype 2 in different areas of Fujian Province for providing scientific evidence for monitoring the swine streptococcus suis serotype 2 .We observed and analysed the corelated characters of bacteria designated as PFJ07isolated from Fujian province, such as bacterial colony, morphology , biochemistry , drugsensitivity test and virulence. The result showed that the shape, cultural and biochemical characters of PFJ07 were basically coincided with Streptococcus suis serotype 2, which could causeβ-hemolysis and lead mouse to death in fory-eight hour.Then a couple of specific primers were designed and composed, which based on the capsular genes sequence of Streptococcus suis serotype 2, then we used PFJ07 as templates to amplify successfully one specific DNA fragment, the length of which was 675 bp, all the experimental and positive bacteria were amplified the same band by PCR assay, however, all non-Streptococcus suis serotype 2 and negative bacteria did not show any reaction. Through optimizing the condition of PCR assay, we determined the detection sensitivity of the thalli's templates and its genomic DNA templates, The reslut suggested that the method of detection was specific and sensitive, the sensitivitiy of which was 100 cfu and 50pg respectively, and that, the method for using the thalli's as templates was simple and convenient. Sequence analysis of the specifical 675bp DNA fragment cloned to T vector showed that the nucleotide homology compared with stavectorsequence of Streptococcus suis serotype 2 from genBank achieved to 98%-100% .So PFJ07 was difinited as Streptococcus suis serotype 2 and designated as SS2PFJO7. We reported firstly that Streptococcus suis serotype 2 existed in Fujian province.Next, We used the commercial antibody detection of Streptococcus suis serotype 2 to investigate and analyse 1347 serum samples from 77 pig farms in 9 areas of Fujian province. The result showed that the positive percentage of panel antibodies in each piggery was greatly differentation from 0 % to 94%; The range of positive piggery in each areas was from 22% to 100%; the total rate of positive in all piggery was 53%; The result suggested that the epidemic focus of Streptococcus suis serotype 2 had been existed in piggery of Fujian, parts of which has the possibility of being infected by Streptococcus suis serotype 2, and the risk of being infected by Streptococcus suis serotype 2 existed in all areas of Fujian.These studies are the foundation for rapid detection of Streptococcus suis serotype 2, further perfect the animal epidemic disease prevention and control system, satisfied the demand of the early-warning and provide a scientific basis for veterinary stations to formulate effective strategies to prevent and control Streptococcus suis serotype 2.