Characterizations Of Streptococcus Suis Serotype 7 Strains And Putative Virulent Genes Of Streptococcus Suis Serotype 2 Strains

Isolates of Streptococcus suis serotype 7 were characterized by ribotyping, pulsed field gel electrophoresis (PFGE). antibiotic resistance and detection of resistance genes. Suppression subtractive hybridization (SSH) was used between virulent strain HA9801 and avirulent strain 12. Five fragments of putative virulent genes were found by this method. Five pairs of primers were designed according to the sequence of these five fragments. Their distributions in S. suis serotype 2 strains were studied.1 Ribotypings of 103 strains of S. suis serotype 7 were studied. 41 different ribotypings were found and 18 ribotypings among them emerged repeatly. Ribotyping 2 was the main one and 23% strains (24/103) belonged to it. According to 77% similarities, these ribotypings could be divided into two main clusters except three unique ribotypings. No obvious relationship between ribotyping profiles and the clinic origin (meningitis, penumoniae. etc.) of the isolates could be found.2 The Pulse Field Gel Electrophoresis (PFGE) method was used to detect 54 strains of S.suis serotype 7 (inculding 24 strains belong to ribotping 2). Fifty kinds of PFGE profiles were found and they could be divided into two clusters (A and B). Cluster B could be furtherly divided into three clusters (B1, B2 and B3). Isolates strongly related by ribotyping but not identical could be discriminated easily by PFGE. All the isolates from spleen belonged to cluster Bl and most of the isolates from meninges or brain belonged to cluster B. But isolates from lungs were found in all clusters. These results showed that no obvious relationship was found between the clinic origins and PFGE profiles.3 Antibiotic resistance of 103 S. suis serotype 7 strains to 13 antibiotics were studied. Results showed that 40.78% (42/103) strains were resistant to erythromycin, 24.27%(25/103) and 28.16%(29/103) strains were resistant to tetracycline and streptomycin separately. A lot of strains(66 strains) were resistant to not only one kind of antibiotic. S. suis serotype 7 strains were susceptible to ceftiofur, ciprofloxacin, florfenicol, penicillin, trimethoprim and trimethoprim + sulphanamides. Besides, five resistant determinants were detected by PCR method for 25 strains resistant to erythromycin and 29 strains resistant to tetracycline. Results showed that erm (B) was the main erythromycin resistant determinant but tet(M) and tet (O) are the main tetracycline resistant determinants.4 Ribotypings of S.suis serotype 2 strains HA9801 and 12 were deteced. Their ribotypings belonged to 1 and 4 ribotyping separately according to what Rasmussen had done and they had 60% similarities. At the same time, their antibiotic resistance to 13 antibiotics were detected. Strain HA9801 was resistant to streptomycin, tetracycline and sulphamethoxazol but strain 12 was susceptible to all the antibiotics. Strain HA9801 was found to have the tetracycline resistant determinant tet(M).5 SSH was used between virulent strain HA9801 and avirulent strain 12. Five fragments of putative virulent genes were found by this method and they are transcriptional regulators, amino acid permease, ABC transporter and surface anchored protein.6 Five pairs of primers were designed for PCR according to the sequence of these five fragments acquired by suppression subtractive hybridization (SSH). Their distributions in 5. suis serotype 2 strains were studied.