streptokokk

Strepptokokk, or streptokokker as they are sometimes called in Nordic languages, refers to a genus of Gram-positive cocci that typically occur in chains or pairs. They are facultative anaerobes and do not form spores. Streptokokker are common commensals of humans, residing in the upper respiratory tract, oral cavity, and skin, but several species are capable of causing disease.

Taxonomy and ecology are historically based on cell wall components, leading to grouping by Lancefield antigens (for example group A and group B) in addition to other species such as Streptococcus pneumoniae. The genus includes the viridans streptococci, which are a diverse collection of species that colonize the mouth and can contribute to dental plaque and endocarditis. S. pneumoniae is a major respiratory pathogen and a common cause of meningitis and bacteremia, whereas the viridans group is a frequent cause of subacute endocarditis.

Pathogenic potential varies among species. Streptococcus pyogenes (group A) causes pharyngitis, impetigo, cellulitis, scarlet fever, and, in some cases, invasive infections. Streptococcus agalactiae (group B) is an important cause of neonatal sepsis and meningitis and can infect pregnant women. Streptococcus pneumoniae causes pneumonia, otitis media, meningitis, and bacteremia. Viridans streptococci are often implicated in dental caries and in subacute endocarditis, particularly in people with preexisting heart valves.

Diagnosis and treatment rely on culture and Gram staining, with rapid tests used for suspected group A infections. Penicillin and related beta-lactams remain first-line for many streptococcal infections; GAS resistance is uncommon, while pneumococcal resistance exists in some regions. Prevention includes pneumococcal vaccination and, for group B streptococcus, intrapartum antibiotic prophylaxis to reduce neonatal disease.