Group A Streptococcus

Group A Streptococcus (GAS) or Streptococcus pyogenes, affects an estimated 800 million people each year. Most of the resulting estimated 639,000 annual deaths are related to rheumatic heart disease (RHD) and its complications. Resource-limited areas account for the vast majority of cases, although outbreaks still occur in industrialized countries. GAS has several mechanisms to avoid phagocytosis, including prevention of opsonization and the use of surface proteins to block complement fixation. The mechanisms behind the immunologic phenomenon are not well understood. Clinical presentations range from benign, short-lived impetigo or pharyngitis through to lifelong RHD. In its most invasive form, GAS can cause a rapidly progressive, often lethal infection: streptococcal toxic shock syndrome. S. pyogenes remains universally sensitive to penicillin, which is the mainstay of treatment.