Department of Bioresource Science, Graduate School of Agricultural Science, Kobe University, Rokko-dai 1-1, Nada-ku, Kobe 657-8501, Japan.
Department of Agrobioscience, Graduate School of Agricultural Science, Kobe University, Rokko-dai 1-1, Nada-ku, Kobe 657-8501, Japan.
Vet Microbiol. 2013 Mar 23;162(2-4):842-849. doi: 10.1016/j.vetmic.2012.11.001. Epub 2012 Nov 22.
To date, Streptococcus suis was divided into thirty-three serotypes based on its polysaccharide capsular antigens. Although 16S rRNA sequence similarities of serotypes 20, 22, 26, and 33 reference strains to the type strain NCTC 10234(T) were below the threshold value of 98.5% to assign them to S. suis species, no strong evidence support to reclassification. Here, their taxonomic identities were determined by DNA-DNA hybridization assays and by partial sequencing of the sodA and recN genes. Our results confirmed that the serotype 20, 22, 26, and 33 reference strains were distantly related to the type strain NCTC 10234(T) and the whole sequence strain P1/7 of S. suis. Moreover, the reference strains of serotypes 20, 22, and 26 were closely related to each other but distinct from the serotype 33 reference strain. Sequencing analyses of sodA and recN of a total 33 serotype reference strains showed that the serotype 20, 22, and 26 reference strains and the serotype 33 reference strain did not fall with not only other serotypes of S. suis, but also other streptococcal species (63 strains of 56 species for sodA and 87 strains of 55 species for recN). The evidence further substantiates the view that the reference strains of serotypes 20, 22, 26 and 33 should be taxonomically removed from S. suis, although their taxonomic designations and determinative phenotypic characteristics are yet to be addressed.
迄今为止，根据其多糖荚膜抗原，已将猪链球菌分为 33 个血清型。尽管血清型 20、22、26 和 33 的参考菌株与 NCTC 10234(T) 型菌株的 16S rRNA 序列相似性低于将它们归类于猪链球菌种的 98.5%的阈值，但没有强有力的证据支持重新分类。在这里，通过 DNA-DNA 杂交试验和 sodA 和 recN 基因的部分测序来确定它们的分类地位。我们的结果证实，血清型 20、22、26 和 33 的参考菌株与 NCTC 10234(T) 型菌株和猪链球菌 P1/7 全序列菌株的亲缘关系较远。此外，20、22 和 26 型参考菌株彼此密切相关，但与 33 型参考菌株不同。对总共 33 个血清型参考菌株的 sodA 和 recN 测序分析表明，20、22 和 26 型参考菌株和 33 型参考菌株不仅与其他猪链球菌血清型不同，而且与其他链球菌种也不同（sodA 为 56 个种的 63 株，recN 为 55 个种的 87 株）。这些证据进一步证实了这样一种观点，即尽管血清型 20、22、26 和 33 的参考菌株的分类名称和决定性表型特征尚待解决，但应从猪链球菌中对其进行分类学去除。
