streptococcal

Streptococcal refers to anything relating to the bacteria of the genus Streptococcus or to diseases caused by these organisms. Streptococci are Gram-positive, non-spore-forming cocci that multiply in chains and are typically facultative anaerobes. They are classified by hemolysis patterns on blood agar (alpha, beta, gamma) and by Lancefield grouping based on C carbohydrate antigens (A, B, C, D, etc.). Many species colonize humans as part of the normal flora, particularly in the oropharynx and skin, but several are important pathogens.

Prominent pathogenic species include Streptococcus pyogenes (group A Streptococcus), Streptococcus agalactiae (group B), Streptococcus pneumoniae (pneumococcus), and various viridans streptococci. S. pyogenes and S. agalactiae are major causes of invasive and noninvasive disease in children and adults; S. pneumoniae is a leading cause of pneumonia, meningitis, and otitis. Viridans streptococci are common causes of dental and invasive endocardial infections.

Clinical manifestations range from pharyngitis, impetigo, erysipelas, and cellulitis to invasive diseases such as necrotizing fasciitis, streptococcal toxic shock syndrome, bacteremia, and meningitis. Post-infectious sequelae include rheumatic fever and post-streptococcal glomerulonephritis after throat or skin infection.

Diagnosis relies on culture of specimens and, for some infections, rapid antigen detection tests or molecular assays. Treatment typically centers on penicillin or amoxicillin; alternatives exist for allergy. In invasive disease, broad-spectrum IV antibiotics and supportive care are used. Vaccination is available for some pneumococcal serotypes but no universal Streptococcus vaccine; prevention relies on prompt treatment of infections and infection-control measures.