Streptococcus pyogenes

Streptococcus pyogenes is a species of Gram-positive, aerotolerant bacteria in the genus Streptococcus. Its cells are non-motile, non-sporing cocci that tend to link together in chains. The species is an infrequent but usually pathogenic part of the human skin microbiota and is the predominant species carrying the Lancefield group A antigen, so it is commonly called group A Streptococcus. It causes group A streptococcal infection, and an estimated 700 million such infections occur worldwide each year; while overall mortality is under 0.1 percent, the more than 650,000 annual severe invasive cases carry a mortality rate near 25 percent. The species name comes from Greek words for a chain of berries and pus-forming, reflecting how its infections often produce pus.