Reappraisal of the taxonomy of Streptococcus suis serotypes 20, 22 and 26: Streptococcus parasuis sp. nov.
In order to clarify the taxonomic position of serotypes 20, 22 and 26 of Streptococcus suis, biochemical and molecular genetic studies were performed on isolates (SUT-7, SUT-286(T), SUT-319, SUT-328 and SUT-380) reacted with specific antisera of serotypes 20, 22 or 26 from the saliva of healthy pigs as well as reference strains of serotypes 20, 22 and 26. Comparative recN gene sequencing showed high genetic relatedness among our isolates, but marked differences from the type strain S. suis NCTC 10234(T), i.e. 74.8-75.7 % sequence similarity. The genomic relatedness between the isolates and other strains of species of the genus Streptococcus, including S. suis, was calculated using the average nucleotide identity values of whole genome sequences, which indicated that serotypes 20, 22 and 26 should be removed taxonomically from S. suis and treated as a novel genomic species. Comparative sequence analysis revealed 99.0-100 % sequence similarities for the 16S rRNA genes between the reference strains of serotypes 20, 22 and 26, and our isolates. Isolate STU-286(T) had relatively high 16S rRNA gene sequence similarity with S. suis NCTC 10234(T) (98.8 %). SUT-286(T) could be distinguished from S. suis and other closely related species of the genus Streptococcus using biochemical tests. Due to its phylogenetic and phenotypic similarities to S. suis we propose naming the novel species Streptococcus parasuis sp. nov., with SUT-286(T) ( = JCM 30273(T) = DSM 29126(T)) as the type strain.
Organization for Advanced Science and Technology, Kobe University, Rokko-dai 1-1, Nada-ku, Kobe, Hyogo 657-8501, Japan.
R
R
Nomoto
Graduate School of Medical and Dental Sciences, Section of Bacterial Phathogenesis, Tokyo Medical and Dental University, Yushima 45-5-1, Bunkyo-ku, Tokyo 113-8510, Japan.
F
F
Maruyama
Research Center for Food Safety, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo 113-8657, Japan.
S
S
Ishida
Research Center for Food Safety, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo 113-8657, Japan.
M
M
Tohya
Research Center for Food Safety, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo 113-8657, Japan.
T
T
Sekizaki
Department of Bioresource Sciences, Graduate School of Agricultural Sciences, Kobe University, Rokko-dai 1-1, Nada-ku, Kobe, Hyogo 657-8501, Japan.
Ro
R
Osawa
D000818:Animals; D004269:DNA, Bacterial / Q000235:genetics; D005798:Genes, Bacterial; D007106:Immune Sera / Q000276:immunology; D008969:Molecular Sequence Data; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012463:Saliva / Q000276:immunology; D017422:Sequence Analysis, DNA; D065288:Serogroup; D013291:Streptococcus / Q000145:classification*; D017011:Streptococcus suis / Q000145:classification*; D013552:Swine / Q000276:immunology
D004269:DNA, Bacterial; D007106:Immune Sera; D012336:RNA, Ribosomal, 16S