Title Pathogenomics of Streptococcus ilei sp. nov., a newly identified pathogen ubiquitous in human microbiome
Author Dong-Wook Hyun1, Jae-Yun Lee1, Min-Soo Kim1, Na-Ri Shin1, Tae Woong Whon1, Kyung Hyun Kim2, Pil Soo Kim1, Euon Jung Tak1, Mi-Ja Jung1, June Young Lee1, Hyun Sik Kim1, Woorim Kang1, Hojun Sung1, Che Ok Jeon2, and Jin-Woo Bae1
Address 1Department of Biology, Department of Biomedical and Pharmaceutical Sciences, and Department of Life and Nanopharmaceutical Sciences, Kyung Hee University, Seoul 02447, Republic of Korea, 2Department of Life Science, Chung-Ang University, Seoul 06974, Republic of Korea
Bibliography Journal of Microbiology, 59(8),793-806, 2021,
DOI 10.1007/s12275-021-1165-x
Key Words Streptococcus, Streptococcus ilei, ileum, ileostomy effluent, virulence factor, pathogenicity, viridans group streptococci, mitis group streptococci
Abstract Viridans group streptococci are a serious health concern because most of these bacteria cause life-threatening infections, especially in immunocompromised and hospitalized individuals. We focused on two alpha-hemolytic Streptococcus strains (I-G2 and I-P16) newly isolated from an ileostomy effluent of a colorectal cancer patient. We examined their pathogenic potential by investigating their prevalence in human and assessing their pathogenicity in a mouse model. We also predicted their virulence factors and pathogenic features by using comparative genomic analysis and in vitro tests. Using polyphasic and systematic approaches, we identified the isolates as belonging to a novel Streptococcus species and designated it as Streptococcus ilei. Metagenomic survey based on taxonomic assignment of datasets from the Human Microbiome Project revealed that S. ilei is present in most human population and at various body sites but is especially abundant in the oral cavity. Intraperitoneal injection of S. ilei was lethal to otherwise healthy C57BL/6J mice. Pathogenomics and in vitro assays revealed that S. ilei possesses a unique set of virulence factors. In agreement with the in vivo and in vitro data, which indicated that S. ilei strain I-G2 is more pathogenic than strain I-P16, only the former displayed the streptococcal group A antigen. We here newly identified S. ilei sp. nov., and described its prevalence in human, virulence factors, and pathogenicity. This will help to prevent S. ilei strain misidentification in the future, and improve the understanding and management of streptococcal infections.