Biological And Genetic Characterization Of Streptococcus Suis Type 2 Isolates From Slaughter Pigs

Streptococcus suis is an important pathogen that can cause meningitis, endocarditis, arthritis and other infections in pigs throughout the word. Thirty-five serotypes based on capsular antigens are currently known. Serotype 2 is the most virulent and prevalent type and can cause zoonosis. The distribution of Streptococcus suis in slaughter pigs, especially of serotype 2, construction of Streptococcus suis Serotype 2 resource bank and foundation of alarm system are helpful to prevent the Streptococcus suis diseases and ensure the heath of the practitioners.Triplex-PCR assay and biochemical tests were used to examine Streptococcus suis in slaughter pigs. A total of 126 streptococcus suis including 3 serotype 2 strains were isolated from 526 samples. The distribution of Streptococcus suis was visibly different among various regions and the carrier rate varied from 0 (Jiangshan) to 66.2% (Ningbo). Serotype 2 strains are isolated from Xiaoshan in Zhejiang and He'nan. The biological features and presence of major virulence factors of serotype 2 isolated were also examined in this study. The results indicate that there is no significant difference in blochemical tests and In vitro growth profile among different isolated strains. ZH0604 has resistance to five antimicrobials including Ofloxacin, Tetracycline, Doxycycline, Erythromycin and Sulfamethoxazole. The hernolytic characteristic value is highest in 5995 and lowest in ZH0604, which is consistent with the virulence revealed as LD50 in mouse models. The three main virulence factor genes mrp, ef and sly from isolated strains of Streptococcus suis serotype 2 were amplified by PCR using the specific primers designed. Through sequencing and analysis of the nucleotide sequence in these three virulence factor genes, it was demonstrated that the homologies of genes among these serotype 2 isolates were ranged from 98.1% to 100%.In summary, the results in this study on prevalence of Streptococcus suis amd its serotype 2 in clinically healthy adult pigs, Streptococcus suis Serotype 2 strain bank, its pathogenesis and control.