[S5-5] Diversity of β-hemolysins produced by opportunistic streptococci and their pathogenic contribution
Anginosus group streptococci (AGS) and Mitis group streptococci (MGS) are commensal streptococci habitual in the oral cavity of human. Except for typical human pathogen S. pneumoniae, most of the species/strains belonging to AGS and MGS are recognized as an opportunistic pathogen, and clinical importance is often underestimated. However, a part of species/strains belonging to these groups of human origin shows β-hemolysis and two kinds of β-hemolysin are known among them. One is the protein toxin generally called cholesterol-dependent cytolysin (CDC), and another is the homologs of streptolysin S (SLS) that is a post-translationally modified peptide toxin. Interestingly, there are structural- and functional-diversity among the β-hemolysins of AGS and MGS, compared to the representative streptococcal β-hemolysins such as streptolysin O and SLS from Pyogenic group streptococci such as S. pyogenes. Especially, CDCs produced from S. intermedius of AGS and from a part of strains of S. mitis and S. pseudopneumoniae of MGS shows human-specific and -preferential activity, respectively. These specificities thought to be important for the pathogenicity toward human. Based on our studies, I intend to introduce the information on the diversities of the β-hemolysins produced by β-hemolytic AGS and MGS and their contribution to the potential pathogenicity of β-hemolytic AGS and MGS.