The group A streptococcus bacterium (Streptococcus pyogenes, or GAS) is a form of β-hemolytic Streptococcus bacteria responsible for most cases of streptococcal illness. Other types (B, C, D, and G) may also cause infection. Several virulence factors contribute to the pathogenesis of GAS, such as M protein, hemolysins, and extracellular enzymes.
β-hemolysis by S.pyogenes Image source: Linda Johansson et al. Clin Infect Dis. 2010;51:58-65
Streptococcal Pharyngitis and Scarlet Fever – Causes, Symptoms, Diagnosis, Treatment and Ongoing care - A childhood disease characterized by fever, pharyngitis, and rash caused by group A β-hemolytic Streptococcus pyogenes (GAS) that produces erythrogenic toxin Read more: http://health.tipsdiscover.com/streptococcal-pharyngitis-scarlet-fever-causes-symptoms-diagnosis-treatment-ongoing-care/#ixzz2ls8YyBI5