Streptococcus B95.-

Author: Prof. Dr. med. Peter Altmeyer

Co-Autor: Prof. Dr. med. Sören Gatermann

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Last updated on: 11.04.2021

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Definition
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The genus Streptococcus consists of numerous species of gram-positive cocci, which are stored in chains or pairs. It is composed of species that mostly belong to the normal flora of human skin and mucosa, and predominantly have a beneficial effect on host physiology. Group A streptococci are frequent colonizers of the pharynx (in 15-20% of children), group B streptococci frequently colonize the lower gastrointestinal tract.

Human pathologically significant are mainly groups A (Streptococcus pyogenes) and groups B (Streptococcus agalactiae) as well as groups C, F and G. The cell wall of beta-hemolytic streptococci shows the typical structure of gram-positive bacteria. In addition to the C-substance (C=engl. carbohydrate) S. pyogenes possesses cell wall components which are necessary for its virulence:

  • M-protein, a highly variable fibrillar surface protein. The M protein has a highly specific toxicity to granulocytes and platelets. Due to its different antigenicity, > 80 variants can be distinguished. The M protein has a sequence homology to keratin 17, which could play a role in streptococcal-induced infectious allergic dermatoses (e.g. in psoriasis vulgaris).
  • Protein F may function as an adhesin.
  • The bound C5a peptidase protects the microorganism from the immune system by cleaving opsonins.
  • Hyaluronidase, streptodornase, streptokinase, pyrogenic proteases (Streptococcal pyrogenicexotoxin, SPE-A and SP-E), as so-called "spreading factors" promote the diffuse uninhibited progression of the infection in the tissue (e.g. in phlegmonous processes).
  • Erythrogenic toxins (ET -A, B, C): In case of colonisation in wound cavities, foreign bodies or on the skin, an uninhibited formation of erythrogenic toxins (ET -A, B, C) can occur, since the body's own immune defence has no access to them. ET-A and ET-C lead to the classic exanthema in scarlet fever and streptococcal toxic shock syndrome (STSS).

General definition
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The classification is based on various biochemical criteria:

Hemolysis behavior on blood agar (alpha, beta, gamma):

  • alpha-hemolysis (greening streptococci): incomplete hemolysis by reduction of hemoglobin to biliverdin-like substances. Among the alpha-haemolytic streptococci there are two clinically important pathogensStreptococcus

    pneumoniae or pneumococci (diplococci!) and Streptococcus viridans

    (a representative of the viridans group is Streptococcus sanguinis, a facultative anaerobic germ of the oral flora).
  • beta-hemolysis: hemolysis yard around colonies (strepotococci secrete hemolysins that completely dissolve erythrocytes). Streptococcus pyogenes is the typical representative.
  • gamma-haemolysis: no haemolysis activity.

Lancefield typing of beta-hemolytic stre ptococci: Beta-hemolytic streptococci are further subdivided according to the Lancefield classification. This classification, which dates back to biologist Rebecca C. Lancefield in 1933, distinguishes > 20 groups of streptococci. It is based on the serological detection of the different antigenicity of the C-substance, a cell wall polysaccharide in the bacterial wall. According to Lancefield, the individual serogroups are named with capital letters (groups A-T). Streptococci of serogroup A(Streptococcus pyogenes) occur in more than 80 variants due to the different antigenicity of the M-protein. Viridans streptococci ("oral streptococci") do not use this classification. They are predominantly α-hemolytic and usually lack the corresponding polysaccharides that act as antigens. Streptococcus agalactiae has the B antigen of the C substance. The bacteria are infectious agents in animals (udder infections in cows). In humans, this streptococcal species occurs as a colonizer of the intestinal tract and vagina. It can be transmitted perinatally and lead to invasive infections.

For the clinical assessment of a streptococcal infection, "antibiotic susceptibility" is of great importance. Streptococci are (in Germany) mostly sensitive to penicillin G. Other common antibiotics for the treatment of streptococcal infections are

are aminopenicillins (ampicillin and amoxicillin), macrolides (e.g. erythromycin) and cephalosporins (e.g. ceftriaxone or cefuroxime).

Pathogen
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Gram-positive cocci growing in chains under aerobic and anaerobic conditions (facultative anaerobic). The grouping of beta-hemolytic streptococci according to the classification published and named by Rebecca Lancefield in 1933 was based on different specific carbohydrate antigens(C-substance - C= carboanhydrate) of the cell wall.

The genus Streptococcus is composed of numerous species, most of which belong to the normal flora of human skin and mucosa. Group A streptococci are frequent colonisation germs of the pharynx (in 15-20% of children), group B streptococci frequently colonise the lower gastrointestinal tract.

Human pathologically significant are mainly groups A (Streptococcus pyogenes) and groups B (Streptococcus agalactiae) as well as groups C, F and G. The cell wall of beta-hemolytic streptococci shows the typical structure of gram-positive bacteria.

In addition to the C substance, S. pyogenes has additional cell wall components that are necessary for its virulence:

  • M-protein, a highly variable fibrillar surface protein. The M protein has a highly specific toxicity to granulocytes and platelets. Due to its different antigenicity, > 80 variants can be distinguished. The M protein has a sequence homology to keratin 17, which could play a role in streptococcal-induced infectious allergic dermatoses (e.g. in psoriasis vulgaris).
  • Protein F may function as an adhesin.
  • The bound C5a peptidase protects the microorganism from the immune system by cleavage of opsonins.
  • Hyaluronidase, streptodornase, streptokinase, pyrogenic proteases (Streptococcal pyrogenicexotoxin , SPE-A and SP-E), as so-called "spreading factors" promote the diffuse uninhibited progression of the infection in the tissue (e.g. in phlegmonous processes).
  • Erythrogenic toxins (ET -A, B, C): In case of colonisation in wound cavities, foreign bodies or on the skin, an uninhibited formation of erythrogenic toxins (ET -A, B, C) can occur, since the body's own immune defence has no access to them. ET-A and ET-C lead to the classic exanthema in scarlet fever and streptococcal toxic shock syndrome (STSS).

Clinical picture
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Diagnosis
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Fact Sheet:

Defin: Large group of bacteria with human and animal pathogenic representatives. The classification is based on various biochemical criteria:

  • Hemolysis behavior on blood agar (alpha, beta, gamma):
    • alpha-haemolysis (greening streptococci): incomplete haemolysis by reduction of haemoglobin to biliverdin-like substances.
    • beta-haemolysis: haemolysis around colonies
    • gamma-hemolysis: no hemolysis activity.
  • Lancefield typing (of beta-hemolytic streptococci):

    • Beta-hemolytic streptococci are further subdivided according to the Lancefield classification. This goes back to the biologist Rebecca C. Lancefield in 1933. It distinguishes more than 20 groups of streptococci; based on serological evidence of differential antigenicity of C-substance, a cell wall polysaccharide in the bacterial wall.
    • According to Lancefield, the individual serogroups are named with capital letters (groups A-T). Streptococci of serogroup A (Streptococcus pyogenes) occur in more than 80 variants due to the different antigenicity of the M-protein.
    • This classification is not used for viridans streptococci ("oral streptococci"). They are predominantly α-hemolytic, usually lacking the corresponding polysaccharides that act as antigens.
    • Streptococcus agalactiae has the B antigen of the C substance. The bacteria are infectious agents in animals (udder infections in cows). In humans, this streptococcal species occurs as a colonizer of the intestinal tract and vagina. It can be transmitted perinatally and lead to invasive infections.
  • Clin:

Therapy
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Penicillin G is the drug of choice (e.g. Penicillin Grünenthal). Other penicillins, carbapenems, cephalosporins, macrolide antibiotics, clindamycin and glycopeptide antibiotics are also effective, but in the case of extensive soft-tissue infections, even high penicillin doses cannot guarantee freedom of appearance. In these cases a parenteral combination therapy, e.g. with clindamycin, is necessary.

Note(s)
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In daily paxis, a classification based on hemolysis behavior, antigenic structure, and oxygen demand has proven useful: A distinction is made:

Literature
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  1. Angel CS et al (1994) Degradation of C3 by Streptococcus pneumoniae. J Infect Dis. 170:600-608.
  2. Barlow T (1883) Erythema marginatum. Br Med J 509
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  4. Jedrzejas MJ (2004) Extracellular virulence factors of Streptococcus pneumoniae. Front Biosci 9:891-914. review.
  5. Kadavath S et al.(2015) Adult-onset Still's disease-pathogenesis, clinical manifestations, and new treatment options. Ann Med 47:6-14
  6. Lähteenmäki K et al (2001) Bacterial plasminogen activators and receptors. FEMS Microbiol Rev 25:531-552.
  7. Lehndorff H, Leiner C (1922) Erythema annulare. Z Kinderheilkd (Berlin) 32: 46
  8. Martin WJ et al (2015) Post-infectious group A streptococcal autoimmune syndromes and the heart.Autoimmune Rev 14:710-725.
  9. Nitsche-Schmitz DP et al (2007) Group G streptococcal IgG binding molecules FOG and protein G have different impacts on opsonization by C1q. J Biol Chem 282:17530-17536.
  10. Rullan E et al (2001) Rheumatic fever. Curr Rheumatol Rep 3: 445-452.
  11. Schäkel K et al (2016) Pathogenesis of psoriasis. Dermatologist 67: 422-432
  12. Timmer AM et al (2009) Streptolysin O promotes group A Streptococcus immune evasion by accelerated macrophage apoptosis. J Biol Chem 284:862-871.
  13. Walz B et al. (2015) Fever, skin changes, myalgia--from early symptom to diagnosis. Dtsch Med Wochenschr 140:1137-1144.

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Please ask your physician for a reliable diagnosis. This website is only meant as a reference.

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Last updated on: 11.04.2021