Isolation, Identification And Characterization Of Streptococcus Suis From Different Districts Of Hubei Province, China

Streptococcus suis is an important porcine pathogen, causing arthritis, meningitis, septicemia, bronchitis in pigs and pleurisy, septicemia, even death in humans. In recent years, the morbidity and mortality of the disease have been to rise gradually and the live safety of special employee is threatened. In accordance with the difference of capsular antigen in S. suis, 35 kinds of serotypes have been found. S. suis serotype 2 is worldwide a serotype isolated frequently, then S. suis serotype 1, 7, 9 and 1/2. Interaction between pathogenicity virulenee factors of this bacterium is correlated. For studies on serotype, distribution of virulence gene, antimicrobial susceptibility and pathogenicity of strains of Streptococcus suis form different districts of Hubei province, we did reseaeh as follow:1. 30 S. suis strains were isolated and identified from pigs of "high fever syndrome" collected from these areas such as Daye, Tiartmen, Jianli and so on in Hubei province by ATB(?) Rapid ID 32 Strep and PCR typing, including 20 serotype 7 strains, 2 serotype 9 strains, 8 other serotype strains, no serotype 1 strain or serotype2 strain. Serotype 7 is epidemic and highly isolating rate in Jianli principally, in Yangxin, Hongshan, Hong' an, Tianmen, Hannan posteriorly. Serotype 9 is epidemic in Shishou principally. Other serotypes (no serotype 1 or serotype2) are epidemic in Zigui, Songzi and so on.2. The sequences of cps7H gene, cps9H gene and gdh gene were compared with those of other S.suis strains published in GenBank by BLAST. Sequence homology between all strains and mostly sequences reported was 98～100%, which showed that they have the most homologous. But Sequence homology between serotype 9 strains and strains from Shanghai is just 61%, which showed that they have comparatively large variability.3. According to the correlated literatures: 6 pairs of primers to the major virulence genes were designed, of which were based on the virulenee genes mrp, epf sly, orf2, gdh, fpbs. By PCR testing, the phenotypes of 30 Streptococcus suis strains were: mrp+ (3.3%), epf+(33.0%), sly+(16.7%), orf2+ fbps+(43.3%), gdh+(100.0%). It was possible that virulence gene regionnality distribution of S.suis in Hubei province was different from other countries and areas of the world. The result of mice experiment indicated that the virulence between different strains was difference, and the ogenicity of some strains were comparatively high, including serotype 7, serotype 9 and other serotype strains(non serotype 1 or serotype 2).4. The observation of Histopathology showed that the injected mice had symptom of acute septicemia, following with nephritis, pneumonia and impairment of spleen and lymphaden. The result indicated that S.suis serotype 7, serotype 9 and other serotypes the has the determinate pathogenicity besides serotype 2 reported universally.5. Antimicrobial susceptibility of all test strains in Hubei province were highly drug fast and very different. subtotal strains were resistance to general all purpose drugs, such as oxolinic acid, arilin, tylosin, cillimycin, cyclomycin, streptomycin and so on, but sensitive to pyostacine, rifampicin, amoxicillin, apramycin, complex amoxicillin and so on. The results would provide reference for clinical medication.