USE OF RIBOTYPING AND HEMOLYSIN ACTIVITY TO IDENTIFY HIGHLY VIRULENT STREPTOCOCCUS-SUIS TYPE-2 ISOLATES

Nineteen Streptococcus suis type 2 isolates were evaluated for their v irulence in pigs and mice, Of these, seven were determined to be highl y virulent in pigs on the basis of clinical sign scores and gross path ology and histopathology results, Clinical sign scores correlated with gross pathology and histopathology scores at P equal to 0.004 and P e qual to 0.009, respectively, The virulence of highly virulent isolates in pigs compared somewhat with virulence in mice, but the correlation was not significant. No correlation of virulence was noted among the moderately virulent and avirulent isolates in pigs and mice, Chromosom al DNAs from all S, suis isolates were evaluated by PstI, PvuII, EcoRI , and Haem restriction enzyme digestion followed by hybridization with a digoxigenin-11-dUTP-labeled cDNA probe transcribed from 16S and 23S rRNAs from Escherichia coli, The hybridization patterns (ribotypes) v aried depending upon the enzyme used, but a significant number of isol ates determined to be highly virulent in pigs had unique hybridization patterns compared with those of the moderately virulent and avirulent isolates (P = 0.002), In addition, hemolysin activity showed a high c orrelation to virulence (P = 0.00008) and ribotype (P = 0.002).