Streptococcus pyogenes (group A β-hemolytic streptococcus, GABHS) is a gram-positive cocci identified as a human pathogen. It is responsible for infections of varying degrees of severity. Some of them are inviasive invections (they develop in physiologically sterile tissues) and despite the treatment they are characterized by high mortality. Streptococcus pyogenes infection usually leads to pharyngitis (strep throat) and tonsillitis (angina) or impetigo (superficial skin infection). Both forms of infections are relatively benign, but untreated or treated incorrectly may lead to complications. In the case of angina possible complications encompass abscesses (peritoneal abscess, peritonitis, lymphadenitis, otitis media, sinusitis, less commonly pneumonia, cerebro-spinal mucosa). In the case of skin infections complications include infection of subcutaneous and superficial lymphatic vessels. At 2-3 weeks after untreated pharyngitis, severe rheumatic complications may appear in the form of rheumatic fever. It is an autoimmune disease that manifests itself as an inflammation of the myocardium and arthritis and is responsible for the acquired heart defects. Acute glomerulonephritis may be another non-purulent complication. The infection may also lead to septicemia and streptococcal toxic shock syndrome.
In humans carrying this streptococcus, Streptococcus pyogenes occurs mainly in the upper respiratory tract and on the skin, and may also colonize the genitals and the anal area. It is estimated that 12 to 23% of schoolchildren and 5% of adults are carriers of Streptococcus pyogenes. The infection can occur by droplet route, by contact with secretions from the mucous membranes of the patient or by contact with the affected skin. The incubation period is 2-5 days for pharyngitis and tonsillitis and 5-7 days for skin infections.