SLS is a non-immunogenic, oligopeptide, oxygen-stable, thermolabile cytolysin,
responsible for the β-hemolysis on blood agar medium. It is produced when cells are in
stationary phase of growth (Sierig et al., 2003). SLS is one of the most potent cytotoxins
known. It has a broad spectrum cytolytic activity on the membranes of erythrocytes,
leukocytes, platelets and sub-cellular organelles such as lysosomes and mitochondria
(Bisno et al., 2003; Nizet, 2002). The genetic locus identified for production of SLS is
the sag operon, which includes nine genes sagA-sagI. SLS is effective in forming
transmembrane pores and causing lysis when GAS is in contact with target cells. SLS
also promotes resistance to phagocytic killing by exerting cytocidal activity on
neutrophils (Kwinn & Nizet, 2007).