7型猪链球菌的分离鉴定和特性研究

17 isolates of Streptococcus suis serotype 7 from diseased pigs with "High Fever Syndrome" in Hubei province, China, were characterized by automatic biochemical identification, PCR typing, antimicrobial susceptibility testing, PCR test of virulence gene, animal test assay and pathobiology. The results of automatic biochemistry identification indicated that all isolates belonged to serotype 2, but serotype 7 by PCR typing. Sequence homology of all strains was 100% as sequences reported The distribution of virulence gene test showed that mrp+ (0.0%), epf+(11.8%), sly+orf2+(17.6%), fbps+(29.4%), gdh+(100.0%) of 17 serotype 7 strains. Antimicrobial susceptibility of all test strains to 28 antimicrobial agents were very different, but 15(88.2%) strains were resistance to amoxicillin , compound amoxicillin respectively and 17(100%) strains were susceptible to erythromycin. Result of mouse virulence test showed that virulence of strain HB6, strain HB8, strain HB9 was highly than others. In histopathology, congestion and hemorrhage of main organs of diseased pigs and infection mice were obvious in this research. In conclusion, S.suis serotype 7 had existed in Hubei province and there was polyinfection of serotype 7 in pigs with "high fever syndrome" whose mainly pathogen was PRRSV.