Streptococcus taoyuanensis sp. nov., a Novel Species Isolated from a Patient with Bacteremia

Streptococcus spp. are important opportunistic pathogen of bacteremia in both immunocompetent and immunosuppressed patients. A streptococcal strain, designated ST2^T, was isolated from the blood specimen of a bacteremic patient. Comparative analyses of 16S rRNA, rpoB and groEL gene sequences demonstrated that the novel strain ST2^T is a member of the genus Streptococcus. Based on of 16S rRNA gene sequence similarities, the type strains of Streptococcus (S.) parasanguinis (99.2%), S. ilei (98.8%), S. oralis subsp. oralis (97.6%), S. australis (97.5%) and S. sanguinis (97.5%) were the closest neighbours to strain ST2^T. The housekeeping gene sequences (rpoB and groEL) similarities of strain ST2^T to these closely related type strains were 80.4-97.4%, respectively. The complete draft genome of strain ST2^T consisted of 2,155,906 bp with a G + C content of 42.0%. Strain ST2^T has an average nucleotide identity (ANI) value of 94.1 and 81.3% with S. parasanguinis ATCC 15912^T and S. ilei I-G2^T, respectively. The highest in silico DNA-DNA hybridization value with respect to the closest species S. parasanguinis was 55.6%, below the species cut-off of 70% hybridization. The primary cellular fatty acids of strain ST2^T were C_16:0, C_18:1 ω9c, C_18:0 and C_14:0. Based on biochemical criteria and molecular genetic evidence, it is proposed that strain ST2^T be assigned to a new species of the genus Streptococcus as Streptococcus taoyuanensis sp. nov. The type strain of Streptococcus taoyuanensis is ST2^T (=NBRC 115928^T = BCRC 81374^T) as the type strain.