New Molecular Typing Method Of S. Suis Strains And Antimicrobial Susceptibility Test In Healthy Pigs

In previous research, two invasive Chinese strains, S. suis 98HAH33 and S. suis 05ZYH33 were clustered into MLST ST7. However, the molecular characteristic of these two strains is inconsistent with other strains in MLST ST7. In this research, six housekeeping gene and CPS fragments of five invasive S. suis strains was obtained and the fragments were concatenated together as C76and C77. Then the concatenated sequences were used for phylogenetic tree analysis using DNA star software to resubtyping these popular S.suis isolates. Eight phylogenetic trees were obtained in this study and analysis of these trees revealed that the invasive S. suis strains isolated in China all belong to MLST ST1, and they all have a close relationship with S. suis 1/7. At the same time,they differed obviously from S. suis BM407 ,which was also belongd to MLST ST1. this result is in agree with the the molecular characteristic and genome analysis of these strains.In this research, 67 S. suis isolates was isolated from 152 of the tonsils from healthy slaughting pigs that was come from Wuwei, Lanzhou and Qingyang of Gansu province,PRC. Antimicrobial susceptibility test using disk diffusion showed that all of the bacterials isolated were multiple-antibiotic resistant, and for one isolates,it resistance to 16 of the 22 antibiotics detected. PCR was performed to investigat whether these isolates have a 89k pathogenicity island (PAI) 89K which was specific for Chinese SS2 virulent isolates or not.