Streptococci (synonyms: Streptococcus; streptococcal infection; beta-hemolytic streptococci; ß-hemolytic streptococci; ICD-10 A49.1: streptococcal infection of unspecified location) are Gram-positive bacteria arranged in chain form. They belong to the natural bacterial flora of humans as well as mammals, but can also be the trigger of various diseases. Group A streptococci (GAS), for example, are often the cause of infections in the upper respiratory tract. Streptococci can be divided into several different subgroups. One of the most important subdivisions is the Lancefield classification, according to which bacteria are divided into serogroups A to W on the basis of a specific structure. In addition, there are bacteria that cannot be classified into these groups.Serological classification of streptococci (according to Lancefield).
| Serogroup | Species | Hemolysis |
| A | S. pyogenes,S. anginosus group | β(α,γ) |
| B | S. agalactiae | β (γ) |
| C | S. anginosus group,S. dysgalactiae subsp. equisimilis | β(α, γ) |
| D | S. bovis | α |
| F | S. anginosus group | β(α, γ) |
| G | S. anginosus group,S. dysgalactiae subsp. equisimilis | β(α, γ) |
| Miscellaneous | “Greening” streptococci | α(γ) |
| Not typeable | S. pneumoniae | α |
Important representatives of the serogroups are:
- Serogroup A – Streptococcus pyogenes is the most important representative of GAS (group A streptococci); these are responsible for diseases such as tonsillitis (inflammation of the tonsils), scarlet fever, erysipelas (erysipelas; purulent infection of the skin and subcutaneous tissue (subcutis)), impetigo contagiosa (synonym: Impetigo vulgaris; incubation period (time from infection to onset of disease): 2-10 days; less commonly Streptococcus pyogenes; more commonly Staphyloccocus aureus infection): Highly contagious, superficial infection of the skin; otitis media (middle ear infection), pharyngitis (pharyngitis), or necrotizing fasciitis (foudroyant life-threatening infection of the skin, subcutis (subcutaneous tissue), and fascia with progressive gangrene; often involves patients with diabetes mellitus or other conditions that lead to circulatory problems or decreased immune defenses)
- Serogroup B – Streptococcus agalactiae; these are responsible, among other things, for sepsis (blood poisoning), wound and urinary tract infections and neonatal infections
- Streptococcus pneumoniae (not assigned to any serogroup) – they are mainly responsible for pneumonia (pneumonia), otitis media (otitis media) and meningitis (meningitis).
- Oral streptococci (not assigned to any serogroup) – bacteria that are physiologically located in the pharynx, In the gastrointestinal tract and vagina; they are often the causative agents in appendicitis (appendicitis), endocarditis (endocarditis) and dental caries.
- Enterococci (not assigned to any serogroup) – they are physiologically located in the intestine; are often pathogens of urinary tract infections.
Pathogen reservoir is the human being. Transmission of the pathogen (route of infection) is fecal-oral (infections in which pathogens excreted with feces (fecal) are absorbed through the mouth (oral); smear infection), for example, hand contact with contaminated surfaces, or aerogenic (droplet infection in the air).Indirect infections via food are described, but very rare. The duration of infectivity (contagiousness) can be up to 3 weeks for acute streptococcal infections that have not been specifically treated, and longer for those with purulent secretions.After initiation of effective antibiotic therapy, contagiousness for throat infections ceases after 24 hours. Course and prognosis: As a rule, infections with streptococci can be treated well with antibiotics. If therapy is not adequate, complications such as rheumatic fever or glomerulonephritis (kidney disease, with inflammation of the kidney filter cells) may occur.