Streptolysin S (SLS; sagA), is a cytolytic virulence factor which is a member of the thiazole/oxadole-modified microcin (TOMM) family. This cytolysin is a post-translationally modified peptide was synthesized through a natural evolutionary pathway. SLS is responsible for Streptococcus pyogenes' β-hemolytic appearance when grown on blood agar plates.