Streptococcus nasisuis sp. nov., Isolated from a Pig with Respiratory Illness.

Strain ZY1909104T was isolated from the nasal cavity of a pig with respiratory illness in Yunnan Province, south-west China, and characterized to determine its taxonomic status. The strain was Gram-stain-positive, oxidase- and catalase-negative, non-motile, facultative anaerobic coccus arranged in pairs. The strain was capable of growth at temperature range of 22–43 °C (optimum 37 °C), at pH level 6.0–9.0 (optimum pH 7.0) and in the presence of 0–1.5% (w/v) NaCl (optimum 1.0% NaCl). Phylogenetic analysis of the 16S rRNA gene sequences showed that the strain formed a sister branch with Streptococcus suis CCUG 7984T within the genus Streptococcus. Phylogenomic analysis of the single-copy gene sequences further revealed that the strain formed a sister branch with S. suis CCUG 7984T and S. parasuis DSM 29126T within the genus Streptococcus. The strain showed the highest levels of similarity to type strains of the genus Streptococcus, with 97.9% 16S rRNA gene sequence similarity, 80.2% orthologous average nucleotide identity (OrthoANI) and 83.9% average amino acid identity (AAI) to S. suis CCUG 7984ᵀ, and a digital DNA-DNA hybridization (dDDH) value of 38.0% to S. porci DSM 23759ᵀ. These values were lower than the threshold values for demarcation of a new species. The genomic G + C content was 42.8%. The strain shared the Lancefield group D antigen, major fatty acids (> 5 %) C12:0, C14:0, C16:0, C18:0 and C18:1 ω9c, and major polar lipids phosphatidylglycerol (PG), monogalactosyldiacylglycerol (MGDG), phosphatidylcholine (PC), ether-linked phosphatidylcholine (EtherPC) and phosphatidylinositol (PI) with the most closely related type strains S. suis CCUG 7984T and S. parasuis DSM 29126T. Based on these phenotypic and genotypic characterizations, strain ZY1909104T belongs to a novel species of the genus Streptococcus, for which the name Streptococcus nasisuis sp. nov. is proposed. The type strain is ZY1909104T (= NBRC 116581T=CCTCC AB 2023270T).