Detection of virulence-associated factors of Streptococcus suis serotype 2 by PCR assay in Hebei, Province of China

Streptococcus suis is the causative agent of a contagious porcine disease, characterised by pneumonia, arthritis, septicemia, pericarditis and meningitis. It also has a zoonotic character and can be isolated from a wide variety of mammals, including man. The objective of this study was to investigate the distribution of virulence-associated factors of the S. suis serotype 2 strains in Hebei Province of China. Six virulence genes were detected by PCR amplification for 22 strains of S. suis serotype 2 isolated from pigs in Heibei province and they were: the glutamate dehydrogenase gene (gdh), the capsular polysaccharides gene (cps), the muramidate-released protein gene (mrp), extracellular factor (ef), the suilysin gene (sly) and the virculence-associated sequence (orf2). The results showed that there were 6 strains (27%) which contained the six virulence genes and 9 strains (41%) which contained five of the six virulence genes above mentioned. The rest of the strains (32%) lacked of someone of the virulence genes. These results showed that the prevalent strains of S. suis serotype 2 were virulent strains which contain all six virulence factors and the main virulent genotype in China is which contained five of the six virulence genes.   Key words: Streptococcus suis serotype 2, virulence-associated factor, PCR.