Establishment And Application Of Detection Methods For Streptococcus Suis Type2

Streptococcus suis(SS) infections are considered a major worldwide problem in the swine industry. It is associated with a variety of conditions including meningitis, septicaemia, polyserisitis, arthritis, endocarditis and pneumonia. It has also been isolated from cases of rhinitis and abortion. Some types, mainly2,can occasionally cause meningitis in people as well as pigs. Fortunately human cases are rare. An important pig and human S.suis outbreak in China in summer2005, leading to39human death cases. So, it is very urgent and important to establish and apply detection methods for Streptococcus suis.1. Detection methods for S. suis type2in pig productsNew selective and differential media were developed for detection of S. suis type2in pig products. After homogenized with Todd-Hewitt broth(dilution factor of1:10), samples were cultured in THB containing sodium azide (400micrograms/ml), crystal violet (0.4micrograms/ml) and sodium sulfite((200micrograms/ml) for18hours at37℃.Then,it was isolated on the differential agar consisted of Colombia agar,5%defibrinated sheep blood with addition of sodium azide (200micrograms/ml), crystal violet (0.2micrograms/ml) and. sodium sulfite((100micrograms/ml).The isolates were identified by molecular,serolgcial and chemmical method.2. Production of typing antisera for S. suis type2ATCC43765was used for the production of antisera. To obtain antigens containing much capsular material for immunization, the strain was subcultured three times in Todd-Hewitt broth with6h incubation,5ml of the last6-h subculture was inoculated into50ml of a prewarmed broth, which was incubated for only2h. For the production of antisera, rabbits weighing3kg were given three injections per week of increasing concentrations of bacteria for4weeks. Antisera were titrated by using the tube agglutination test, and the agglutination titer of the antisera was128. The antisera did not agglutinated with other streptococci except S.suis type2. So, the antisera can be used to type S. suis type2。3. Detection of suilysin gene of Streptococcus suis type2by PCRStreptococcus suis type2is an important pathogen of swine which occasionally infects humans as well, and suilysin is one of the most important virulence factor. PCR assays were developed for the rapid and sensitive detection of suilysin gene (sly) of Streptococcus suis type2. PCR primers based on the sequence of sly can amplify a495bp PCR product from S.suis type2Strains ATCC43765and Strain HA9801isolated in Jiangsu Province in1998, however, no PCR product was detected from other bacterias。The sensitivity of the PCR assay was250cfuml-1of the bacteria. Digested with Hind Ⅲ, the PCR products could produce314bp and181bp DNA fragments as expected. The sequences of sly PCR products were the same as Z36907showed in GenBank. The results demonstrated that this PCR assay is a rapid, sensitive and specific diagnostic tool for detection of suilysin gene of type2.4. Detection of Streptococcus suis type2from entry-exit pig products in JiangsuAbstract:Entry-exit pig products in Jiangsu were investigated for the presence of Streptococcus suis from2005to2010. Streptococcus suis was found in31of920samples (3.37%), and Streptococcus suis type2was found in17of920samples (1.85%). It suggested that Streptococcus suis was present in pig products, however,the prevelance is low.