The Research Of SS2Infection To Rabbits

Streptococcus suis serotype2is an important pathogen of zoonotic infectious diseases. It can cause meningitis,septicemia,arthritis, bronchopneumonia, pneumonia and unexpected death of pigs and can also cause meningitis of human. Several outbreaks of SS2infection have been reported in China and other countries where pig husbandries are flourishing, which has made substantial economic losses of pig industry. Streptococcus suis serotype2produces many virulence factors such as capsular polysaccharide (CPS), suilysin (SLY), muramidase released protein (MRP), extracellular protein factor (EF) and so on.It can infect animals through enteron, respiratory tract and damaged skins or mucous membranes. The pathogen is infectious to pigs, rabbits, mouse and cavia cobayas,it can also infect human, cattles, sheeps, horses, dogs,cats and so on. In science research, The pathogenicity essays of animals played an important role in the research of bacteria etiology. It can not noly be a standard for assessing virulence of bacteria, but also be used for studying the pathogenicity mechanism. It also played an important role in preventing and controling the disease.The assay chose two strains of SS2which had different virulence factors and were isolated from different places. They were SS2-1and SS2-GN and they were used for infecting rabbits for the pathogenicity research. The assay was divided into several groups including different infecting dose group, different infecting methods group and dynamic testing group. It was expected to explore the pathogenicity regularity of SS2for infecting rabbits and to study the pathogen’s location, quantity and dynamic distribution in the rabbits’tissues.First, fluorescence quantitative real-time PCR (FQRT-PCR) for testing SS2was established. The primer and it’s corresponding Taqman probe for the cps2J and mrp gene sequences of SS2-1were designed. The extracted genomic DNA of SS2was made for the template. The reaction system of fluorescence quantitative real-time PCR was established, which showed fine specificity and sensitivity and quantitative linearity. The assay was arranged for revealing the dependablity between colony count and FQRT-PCR. The artificial distribution of SS2assay was also designed.Second, the research of SS2infection to rabbits as the animal model was progressing. The rabbits was infected109CFU SS2-1by intravenous, intramuscular, subcutaneous injection, cavitas nasi and mouth infection. The Previous four can cause morbility or death while the last one didn’t cause morbility. The rabbits infected by intravenous injection has the severest morbility; The rabbits was infected109、108、107、106、105CFU SS2-1by intravenous injection and108、106CFU SS2-1by intramuscular injection,all the rabbits got morbility and some died. The results of the two groups indicated that infection dose and morbility extent had positive correlation; In another group, The rabbits was infected108CFU SS2-1by intramuscular injection, the tissues was sampled at different time and tested for the pathogen quantity. The result indicated that the pathogen quantity was increasing with time passing, and got to the peak in the period of severest morbility. The rabbits was infected109CFU SS2-GN by intravenous, intramuscular and subcutaneous injection, the previous one caused morbility and death while the post two only caused morbility with no death; The rabbits was infected108CFU SS2-GN by intravenous injection, the tissues were sampled at different time and tested for the pathogen quantity, all the rabbits got morbility and some died. The result was similar with SS2-1.The rabbits infected by SS2had the clinical symptom such as hyperpyrexia (above41℃), downcast, anorexia, lateral decubitus, inability of standing and individual skew head. The tissues had apparent affection, and the pathogen could be isolated from the tissues of the infected rabbits. The pathogen quantity of dead rabbits’ tissues was higher. The spleen had the most pathogen, while the liver, kidney, lung had the less, and the brain, lymph node had the least.The assay demonstrated that SS2-1and SS2-GN was infectious to rabbits, the pathogen had stable pathogenicity. SS2generated stably in rabbits’ body with regularity. So, it’s possible to study SS2’s infection using rabbits as the animal model.