Group A Streptococcus

Group A Streptococcus, or Streptococcus pyogenes, is a bacterium that can cause illnesses ranging from strep throat and scarlet fever to life-threatening invasive infections.

M protein: A surface protein of Streptococcus pyogenes that helps the bacterium resist immune clearance and attach to host tissues. This major virulence factor helps explain how the bacterium avoids phagocytosis.
Scarlet fever: An illness caused by toxin-producing Streptococcus pyogenes, marked by fever and a characteristic widespread rash. It is a recognizable manifestation of toxin-producing strains.
Streptococcus: A genus of spherical, Gram-positive bacteria that commonly grow in chains or pairs. Streptococcus pyogenes is one member of this broad bacterial genus.
Group B Streptococcus: Streptococcus agalactiae, a bacterium associated with neonatal infections and disease in pregnant adults. Its Lancefield group differs from the group A organism, and its clinical risks differ.
Antibiotic stewardship: Coordinated practices that improve antibiotic use to preserve effectiveness and reduce avoidable harm. Accurate diagnosis helps avoid unnecessary antibiotics for viral sore throats while treating confirmed infections.
Streptolysin O: An oxygen-sensitive toxin that forms pores in host-cell membranes and is produced by Streptococcus pyogenes. Its tissue-damaging activity contributes to infection and provokes antibodies measured after illness.
Necrotizing fasciitis: A rapidly progressive infection that destroys fascia and subcutaneous tissue and can be caused by Streptococcus pyogenes. This invasive infection illustrates the organism’s capacity for severe tissue destruction.
Lancefield grouping: A classification system that groups streptococci by carbohydrate antigens in their cell walls. The organism’s group A designation comes from this cell-wall antigen system.
Streptococcus pneumoniae: A bacterium that commonly causes pneumonia, meningitis, and middle-ear infections. It is a major human pathogen in the same genus but is not a group A streptococcus.
Rheumatic heart disease: Chronic damage to heart valves that can result from recurrent or severe rheumatic fever. It is a lasting consequence of immune reactions following group A streptococcal infection.

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