Streptococcus A

A group A streptococcal infection is an infection with group A streptococcus (GAS). Streptococcus pyogenes comprises the vast majority of the Lancefield group A streptococci, and is often used as a synonym for GAS. However, S. dysgalactiae can also be group A. S. pyogenes is a beta-hemolytic species of Gram positive bacteria that is responsible for a wide range of both invasive and noninvasive infections. Infection of GAS may spread through direct contact with mucus or sores on the skin. GAS infections can cause>500,000 deaths per year. Despite the emergence of antibiotics as a treatment for group A β-hemolytic streptococcus, infection of GAS is an increasing problem, particularly on the continent of Africa. Group A β-hemolytic streptococcus can cause infections of the throat and skin. These may vary from very mild conditions to severe, life-threatening diseases. Although it is not completely clear what causes different people to develop different diseases as a result of infection with the same pathogenic bacteria, it is suspected that host phenotypic and epigenetic factors are the source of such variation. Humans may also carry the GAS either on the skin or in the throat and show no symptoms. These carriers are less contagious than symptomatic carriers of the bacteria.