VIRULENT-STRAINS OF STREPTOCOCCUS-SUIS SEROTYPE-2 AND HIGHLY VIRULENT-STRAINS OF STREPTOCOCCUS-SUIS SEROTYPE-1 CAN BE RECOGNIZED BY A UNIQUE RIBOTYPE PROFILE

The ribotype profiles of 42 different Streptococcus suis strains were studied. These strains belonged to five serotypes and differed in thei r virulence for pigs as well as in the expression of the muramidase-re leased protein and the extracellular protein factor, For the ribotypin g, chromosomal DNAs were digested with EcoRI and were hybridized with a 1,066-bp ribosomal DNA probe. The hybridization patterns showed gene tic heterogeneity within and between the serotypes. Pathogenic strains of serotype 2 and highly pathogenic strains of serotype 1 could he re cognized by their unique ribotype profiles. Nonpathogenic strains show ed a high degree of genetic heterogeneity. Moreover, by comparing the 16S ribosomal DNA sequences of a number of S. suis strains, we were ab le to design two DNA probes which specifically hybridized with S. suis strains.