Analysis On Streptococcus Suis By RAPD And Preparation Of Polynalent Inactivity Vaccine Against It

Streptococcus suis infections have risen gradually to become one of the major disease problems in the pork industry. S. suis is responsible for a range of clinical processes including meningitis, neonatal septicemia, bronchopneumonia, arthritis, endocarditic, and reproductive disorders, all of .which have a negative effect on swine production. In order to further identify the serotype of S. suis , this study is to develop the genotyping method of randomly amplified polymorphic DNA (RAPD) for it ,and to prepare the polyvalent inactivated vaccine against S.suis disease.Twenty strains were isolated from the infective pigs in changchun from 2000 to 2001. The biochemical identification for S.suis has been performed by conventional tests and the Lancefield group A~G latex diagnostic kit. The phological and cultural characters indicated that the isolated bacteria belonged to genus Streptococcus. Most of the strains show hemolysis a or ï¿¡ on the sheep blood plate, and the result of biochemical experiment is not stable. The isolates could be agglutinated by the Lancefield group A~G latex diagnostic kit. They were identified as group C, D and G, the three strains of twenty could not been typed. The pathogenecity to mice of the isolates was different. It was demonstrated that group C would not be the only pathogen of S. suis disease in changchun area at present. So it is necessary to produce the polyvalent inactivated vaccine against the S.suis disease.By means of optimizing the reaction conditions and screening the random primers, the genotyping method of RAPD was developed. There are 27 primers to show the polymorphism and the stability, and these strains can produce the stable and complicate PCR fingerprinting. The genetic distance among 20 strains were analyzed by SPSS 10.0, and the polygenetic tree were drawn, which indicates the genetic relationship among the strains. The 20 strains can be divided into 4 clustering groups. The results show that RAPD fingerprint genotyping is suitable for studying on the epidemiology of diseases and genotyping of microbe at molecular level with high-type-ability, powerful discrimination, rapidness and 43simplicity.On the basis of RAPD analysis, four strains were selected as vaccine strain, which possesses stronger toxicity and better immunogenicity. The polyvalent inactivity vaccine against S.suis was developed. Incidence of the disease immuned by the vaccine is 4.2%,and mortality is 1.8%, on the contrary, incidence of the disease unimmuned by the vaccine is 26.8%,and mortality is 13.4%. It is confirmed by the experiments that the vaccine is an effective method to prevent swine from S. suis disease in changchun area. So it is feasible to select vaccine strains by RAPD technique to develop the polyvalent inactivity vaccine against creatural disease.