Astreptokokk

Astreptokokk, in microbiology often referred to as Group A Streptococcus (GAS), denotes Streptococcus pyogenes and related bacteria that belong to Lancefield group A. These are Gram-positive cocci arranged in chains, facultatively anaerobic, catalase-negative, and they form beta-hemolysis on blood agar. GAS is a human-adapted pathogen and is typically transmitted by respiratory droplets or direct contact with infected skin lesions.

Infections caused by GAS range from mild to severe. Common illnesses include pharyngitis (strep throat), tonsillitis, impetigo, cellulitis and erysipelas. GAS can also cause invasive diseases such as necrotizing fasciitis and streptococcal toxic shock syndrome, as well as pneumonia and bacteraemia in vulnerable individuals. Immune-mediated sequelae such as acute rheumatic fever and post-streptococcal glomerulonephritis can follow streptococcal infections, reflecting molecular mimicry and immune complex mechanisms.

Diagnosis relies on clinical presentation supported by laboratory tests. Throat swabs can yield beta-hemolysis on culture and a positive Lancefield Group A antigen. Rapid antigen detection tests provide quick but sometimes less sensitive results. GAS is typically susceptible to penicillin, which remains the treatment of choice; alternative antibiotics are used for penicillin allergy. Prevention emphasizes early diagnosis and treatment of infections, good hand hygiene, and infection control. There is no widely deployed vaccine for GAS as of now, though research continues into vaccines targeting the M protein and other virulence factors.