Streptococcus pyogenes

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Streptococcus pyogenes
Scientific classification
Kingdom:	Bacteria;
Phylum:	Firmicutes;
Class:	Bacilli;
Order:	Lactobacillales;
Family:	Streptococcaceae;
Genus:	Streptococcus;
Species:	S. pyogenes;
Binomial name
	Streptococcus pyogenes; Rosenbach 1884

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview

Streptococcus pyogenes is a Bacilli Lactobacillales that grows in long chains depending on the culture method.^[1] S. pyogenes displays group A antigen on its cell wall and beta-hemolysis when cultured on blood agar plate. S. pyogenes typically produces large zones of beta-hemolysis, the complete disruption of erythrocytes and the release of hemoglobin, and it is therefore called Group A (beta-hemolytic) Streptococcus (abbreviated GAS). Streptococci are catalase -negative.

Serotyping

In 1928, Rebecca Lancefield published a method for serotyping S. pyogenes based on its M protein, a virulence factor that is displayed on its surface.^[2] Later in 1946, Lancefield described the serologic classification of S. pyogenes isolates based on their surface T antigen.^[3] Four of the 20 T antigens have been revealed to be pili, which are used by bacteria to attach to host cells.^[4] Currently, over 100 M serotypes and approximately 20 T serotypes are known.

Pathogenesis

S. pyogenes is the cause of many important human diseases ranging from mild superficial skin infections to life-threatening systemic diseases. Infections typically begin in the throat or skin. Examples of mild S. pyogenes infections include pharyngitis ("strep throat") and localized skin infection ("impetigo"). Erysipelas and cellulitis are characterized by multiplication and lateral spread of S. pyogenes in deep layers of the skin. S. pyogenes invasion and multiplication in the fascia can lead to necrotizing fasciitis, a potentially life-threatening condition requiring surgical treatment.

Infections due to certain strains of S. pyogenes can be associated with the release of bacterial toxins. Throat infections associated with release of certain toxins lead to scarlet fever. Other toxigenic S. pyogenes infections may lead to streptococcal toxic shock syndrome, which can be life-threatening.

S. pyogenes can also cause disease in the form of post-infectious "non-pyogenic" (not associated with local bacterial multiplication and pus formation) syndromes. These autoimmune mediated complications follow a small percentage of infections and include rheumatic fever and acute poststreptococcal glomerulonephritis. Both conditions appear several weeks following the initial streptococcal infection. Rheumatic fever is characterised by inflammation of the joints and/or heart following an episode of Streptococcal pharyngitis. Acute glomerulonephritis, inflammation of the renal glomerulus, can follow Streptococcal pharyngitis or skin infection.

This bacterium remains acutely sensitive to penicillin. Failure of treatment with penicillin is generally attributed to other local commensal organisms producing β-lactamase or failure to achieve adequate tissue levels in the pharynx. Certain strains have developed resistance to macrolides, tetracyclines and clindamycin.

Virulence factors

S. pyogenes has several virulence factors that enable it to attach to host tissues, evade the immune response, and spread by penetrating host tissue layers.^[5] A carbohydrate capsule composed of hyaluronic acid surrounds the bacterium, protecting it from phagocytosis by neutrophils. In addition, the capsule and several factors embedded in the cell wall, including M protein, lipoteichoic acid, and protein F (SfbI) facilitate attachment to various host cells.^[6] M protein also inhibits opsonization by the alternative complement pathway by binding to host complement regulators. M protein found on some serotypes are also able to prevent opsonization by binding to fibrinogen. However, the M protein is also the weakest point in this pathogen's defense as antibodies produced by the immune system against M protein target the bacteria for engulfment by phagocytes. M proteins are unique to each strain, and identification can be used clinically to confirm the strain causing an infection.

S. pyogenes releases a number of proteins, including several virulence factors, into its host:

Streptolysin O and S: These are toxins which are the basis of the organism's beta-hemolytic property. Streptolysin O is a potent cell poison affecting many types of cell including neutrophils, platelets, and sub-cellular organelles. It causes an immune response and detection of antibodies to it; antistreptolysin O (ASO) can be clinically used to confirm a recent infection.

Streptococcal pyrogenic exotoxins (Spe) A and C: SpeA and SpeC are superantigens secreted by many strains of S. pyogenes. These pyrogenic exotoxins are responsible for the rash of scarlet fever and many of the symptoms of streptococcal toxic shock syndrome.

Streptokinase: Enzymatically activates plasminogen, a proteolytic enzyme, into plasmin which in turn digests fibrin and other proteins.

Hyaluronidase: It is widely assumed that hyaluronidase facillitates the spread of the bacteria through tissues by breaking down hyaluronic acid, an important component of connective tissue. However, very few isolates of S. pyogenes are capable of secreting active hyaluronidase due to mutations in the gene that encode the enzyme. Moreover, the few isolates that are capable of secreting hyaluronidase do not appear to need it to spread through tissues or to cause skin lesions.^[7] Thus, the true role of hyaluronidase in pathogenesis, if any, remains unknown.

Streptodornase: Most strains of S. pyogenes secrete up to four different DNases, which are sometimes called streptodornase. The DNases protect the bacteria from being trapped in neutrophil extracellular traps (NETs) by digesting the NET's web of DNA, to which are bound neutrophil serine proteases that can kill the bacteria.^[8]

C5a peptidase: C5a peptidase cleaves a potent neutrophil chemotaxin called C5a, which is produced by the complement system.^[9] C5a peptidase is necessary to minimize the influx of neutrophils early in infection as the bacteria are attempting to colonize the host's tissue.^[10].

Streptococcal chemokine protease: The affected tissue of patients with severe cases of necrotizing fasciitis are devoid of neutrophils.^[11]. The serine protease ScpC, which is released by S. pyogenes, is responsible for preventing the migration of neutrophils to the spreading infection.^[12] ScpC degrades the chemokine IL-8, which would otherwise attract neutrophils to the site of infection. C5a peptidase, although required to degrade the neutrophil chemotaxin C5a in the early stages of infection, is not required for S. pyogenes to prevent the influx of neutrophils as the bacteria spread through the fascia.^[10]^[12]

Diagnosis

Usually, a throat swab is taken to the laboratory for testing. First off, Gram stain is performed to show Gram positive, cocci, in chains. Then, culture the organism on blood agar with added bacitracin antibiotic disk to show beta-haemolytic colonies and sensitivity (zone of inhibition around the disk) for the antibiotic. Then, perform catalase test, which should show a negative reaction for all Streptococci. S. pyogenes is cAMP test negative.

Treatment

The treatment of choice is penicillin. There is no reported instance of penicillin-resistance reported to date, although since 1985 there have been many reports of penicillin-tolerance.^[13]

Macrolides, chloramphenicol, and tetracyclines may be used if the strain isolated has been shown to be sensitive, but resistance is much more common.

Antimicrobial therapy

Streptococcus pyogenes treatment^[14]

(1) Pharyngitis

Preferred regimen: Penicillin-benzathine]] Penicillin 1.2 mU IM once OR Penicillin VK 500 mg PO bd or tid for 10 days.
Alternative regimen (1): Amoxicillin 750 PO bd or tid for 10 days.
Alternative regimen (Penicillin allergy): Erythromycin 500 mg PO bd or tid for 10 days OR (Azithromycin 500 mg, then 250 mg for 5 days, Clarithromycin (Biaxin) 1 g XR/day or 500 mg bd for 10 days. Note: 5-10% isolates are macrolide resistant) OR Cefpodoxime proxetil (Vantin) 200 mg bd for 5 days OR Cefdinir 300 mg bd PO for 5 days OR Cefadroxil 500 mg bd PO for 5 days OR Loracarbef 200 mg PO bd for 5 days.

(2) Skin: erysipelas, lymphangitis, cellulitis

Preferred regimen: Clindamycin 600 mg IV q8h AND Penicillin G G 4 mU IV q4h. (clindamycin to stop toxin production).
Alternative regimen: Penicillin G 2-4 mU IV q4h OR Clindamycin 600 mg IV q8h OR Cefazolin 1-2 g IV q6-8h OR Cefotaxime 2-3 g IV q6-8h OR Ceftriaxone 2 g/day IV OR Vancomycin 15 mg/kg IV q12h.

(3) Soft tissue

Necrotizing fasciitis: surgical consultation for emergent fasciotomy and debridement; repeat debridements usually necessary.

(4) Muscle

Myositis: debirdement

(5) Endometrium

(6) Puerperal sepsis

(7) Lung

pneumonia with or without early bloody effusion Bacteremia

(8) Cardiac are endocarditis (very rare in antibiotic era)

(9) Toxin mediated

Scarlet fever
Toxic shock syndrome

Preferred regimen: Immunoglobulin-G 2 or more doses IV , massive IV fluids (10-20 L/day), Albumin if <2 g/dL, debridement of necrotic tissue.

(10) Non-suppurative complications are rheumatic fever and glomerulonephritis

Note (1): Common infections are bacterial pharyngitis and cellulitis. Rare but devastating are toxic shock syndrome, necrotizing fasciitis.

Note (2): Diagnosis recovery from normally sterile site, ASO antibody response (rheumatic fever),anti-DNAase B (pyoderma). Supportive are positive throat culture or rapid strep antigen test.

Note (3): Cellulitis is very hard to detect Group A streptococcus by culture (needle aspiration or blood culture).

Note (4): Ecologic niche is pharynx. 2-3% of adults colonized, 15-20% school children. Virulence depends on proteins that represent toxins, mimic host macromolecules and after immune responses.

note (5): Predisposing factors: soft tissue (IDU, diabetes, surgery, trauma, varicella, vein donor, lymphedema); pneumonia (influenza), contacts w/ gas (pharyngitis and fasciitis).

Prophylaxis

Acute rheumatic fever prophylaxis

Preferred regimen: Benzathine Penicillin 1.2 mu IM q mo, Penicillin V 250 mg PO bd, Erythromycin 250 mg PO bd until >5 yrs post-acute rheumatic fever and age in 20years.

Recurrent cellulitis, chronic lymphedema prophylaxis

Preferred regimen: Clindamycin 150 mg PO qd OR Trimethoprim-Sulfamethoxaole 1 DS PO qd OR “stand-by therapy” immediate treatment with Penicillin V OR Amoxicillin 500-750 mg PO bd at onset of symptoms.

References

↑ Ryan KJ; Ray CG (editors) (2004). Sherris Medical Microbiology (4th ed. ed.). McGraw Hill. ISBN 0-8385-8529-9.
↑ Lancefield RC (1928). "The antigenic complex of Streptococcus hemolyticus". J Exp Med. 47: 9&ndash, 10.
↑ Lancefield RC, Dole VP (1946). "The properties of T antigen extracted from group A hemolytic streptococci". J Exp Med. 84: 449&ndash, 71.
↑ Mora M, Bensi G, Capo S, Falugi F, Zingaretti C, Manetti A, Maggi T, Taddei A, Grandi G, Telford J (2005). "Group A Streptococcus produce pilus-like structures containing protective antigens and Lancefield T antigens". Proc Natl Acad Sci U S A. 102 (43): 15641–6. PMID 16223875.
↑ Patterson MJ (1996). Streptococcus. In: Baron's Medical Microbiology (Baron S et al, eds.) (4th ed. ed.). Univ of Texas Medical Branch. (via NCBI Bookshelf) ISBN 0-9631172-1-1.CS1 maint: Extra text (link)
↑ Bisno AL, Brito MO, Collins CM (2003). "Molecular basis of group A streptococcal virulence". Lancet Infect Dis. 3 (4): 191–200. PMID 12679262.
↑ Starr C, Engleberg N (2006). "Role of hyaluronidase in subcutaneous spread and growth of group A streptococcus". Infect Immun. 74 (1): 40–8. PMID 16368955.
↑ Buchanan J, Simpson A, Aziz R, Liu G, Kristian S, Kotb M, Feramisco J, Nizet V (2006). "DNase expression allows the pathogen group A Streptococcus to escape killing in neutrophil extracellular traps". Curr Biol. 16 (4): 396–400. PMID 16488874.
↑ Wexler D, Chenoweth D, Cleary P (1985). "Mechanism of action of the group A streptococcal C5a inactivator". Proc Natl Acad Sci U S A. 82 (23): 8144–8. PMID 3906656.
↑ ^10.0 ^10.1 Ji Y, McLandsborough L, Kondagunta A, Cleary P (1996). "C5a peptidase alters clearance and trafficking of group A streptococci by infected mice". Infect Immun. 64 (2): 503–10. PMID 8550199.
↑ Hidalgo-Grass C, Dan-Goor M, Maly A, Eran Y, Kwinn L, Nizet V, Ravins M, Jaffe J, Peyser A, Moses A, Hanski E (2004). "Effect of a bacterial pheromone peptide on host chemokine degradation in group A streptococcal necrotising soft-tissue infections". Lancet. 363 (9410): 696–703. PMID 15001327.
↑ ^12.0 ^12.1 Hidalgo-Grass C, Mishalian I, Dan-Goor M, Belotserkovsky I, Eran Y, Nizet V, Peled A, Hanski E (2006). "A streptococcal protease that degrades CXC chemokines and impairs bacterial clearance from infected tissues". EMBO J. 25 (19): 4628–37. PMID 16977314.
↑ Kim KS, Kaplan EL (1985). "Association of penicillin tolerance with failure to eradicate group A streptococci from patients with pharyngitis". J Pediatr. 107 (5): 681&ndash, 4. PMID 3903089.
↑ Bartlett, John (2012). Johns Hopkins ABX guide : diagnosis and treatment of infectious diseases. Burlington, MA: Jones and Bartlett Learning. ISBN 978-1449625580.

Gallery

Petri dish with Streptococcus pyogenes-inoculated trypticase soy agar on blood agar plate (BAP). From Public Health Image Library (PHIL). ^[1]
Blood agar plate (BAP) inoculated with Group A Streptococcus pyogenes (GAS) bacteria. From Public Health Image Library (PHIL). ^[1]
Blood agar plate inoculated by streaking the surface of the BAP with a non-hemolytic group A Streptococcus pyogenes (GAS) bacteria. From Public Health Image Library (PHIL). ^[1]
Blood agar plate (BAP) inoculated by stabbing the surface of the BAP with a non-hemolytic group A Streptococcus pyogenes (GAS) bacteria (100x mag). From Public Health Image Library (PHIL). ^[1]
Scanning electron micrograph (SEM) revealed a cluster of Gram-positive, beta-hemolytic Group C Streptococcus sp. bacteria. From Public Health Image Library (PHIL). ^[1]
Erythromycin-resistant Group-A Streptococcus (GAS), also known as S. pyogenes, bacteria. From Public Health Image Library (PHIL). ^[1]

References

↑ ^1.0 ^1.1 ^1.2 ^1.3 ^1.4 ^1.5 "Public Health Image Library (PHIL)".

Template:WH Template:WS

[Sherris-1] Ryan KJ; Ray CG (editors) (2004). Sherris Medical Microbiology (4th ed. ed.). McGraw Hill. ISBN 0-8385-8529-9.

[Lancefield_1928-2] Lancefield RC (1928). "The antigenic complex of Streptococcus hemolyticus". J Exp Med. 47: 9&ndash, 10.

[Lancefield_1946-3] Lancefield RC, Dole VP (1946). "The properties of T antigen extracted from group A hemolytic streptococci". J Exp Med. 84: 449&ndash, 71.

[Mora_2005-4] Mora M, Bensi G, Capo S, Falugi F, Zingaretti C, Manetti A, Maggi T, Taddei A, Grandi G, Telford J (2005). "Group A Streptococcus produce pilus-like structures containing protective antigens and Lancefield T antigens". Proc Natl Acad Sci U S A. 102 (43): 15641–6. PMID 16223875.

[Baron-5] Patterson MJ (1996). Streptococcus. In: Baron's Medical Microbiology (Baron S et al, eds.) (4th ed. ed.). Univ of Texas Medical Branch. (via NCBI Bookshelf) ISBN 0-9631172-1-1.CS1 maint: Extra text (link)

[Bisno_2003-6] Bisno AL, Brito MO, Collins CM (2003). "Molecular basis of group A streptococcal virulence". Lancet Infect Dis. 3 (4): 191–200. PMID 12679262.

[Starr_2006-7] Starr C, Engleberg N (2006). "Role of hyaluronidase in subcutaneous spread and growth of group A streptococcus". Infect Immun. 74 (1): 40–8. PMID 16368955.

[Buchanan_2006-8] Buchanan J, Simpson A, Aziz R, Liu G, Kristian S, Kotb M, Feramisco J, Nizet V (2006). "DNase expression allows the pathogen group A Streptococcus to escape killing in neutrophil extracellular traps". Curr Biol. 16 (4): 396–400. PMID 16488874.

[Wexler_1985-9] Wexler D, Chenoweth D, Cleary P (1985). "Mechanism of action of the group A streptococcal C5a inactivator". Proc Natl Acad Sci U S A. 82 (23): 8144–8. PMID 3906656.

[Ji_1996-10] 10.0 ^10.1 Ji Y, McLandsborough L, Kondagunta A, Cleary P (1996). "C5a peptidase alters clearance and trafficking of group A streptococci by infected mice". Infect Immun. 64 (2): 503–10. PMID 8550199.

[Hidalgo-Grass_2004-11] Hidalgo-Grass C, Dan-Goor M, Maly A, Eran Y, Kwinn L, Nizet V, Ravins M, Jaffe J, Peyser A, Moses A, Hanski E (2004). "Effect of a bacterial pheromone peptide on host chemokine degradation in group A streptococcal necrotising soft-tissue infections". Lancet. 363 (9410): 696–703. PMID 15001327.

[Hidalgo-Grass_2006-12] 12.0 ^12.1 Hidalgo-Grass C, Mishalian I, Dan-Goor M, Belotserkovsky I, Eran Y, Nizet V, Peled A, Hanski E (2006). "A streptococcal protease that degrades CXC chemokines and impairs bacterial clearance from infected tissues". EMBO J. 25 (19): 4628–37. PMID 16977314.

[13] Kim KS, Kaplan EL (1985). "Association of penicillin tolerance with failure to eradicate group A streptococci from patients with pharyngitis". J Pediatr. 107 (5): 681&ndash, 4. PMID 3903089.

[14] Bartlett, John (2012). Johns Hopkins ABX guide : diagnosis and treatment of infectious diseases. Burlington, MA: Jones and Bartlett Learning. ISBN 978-1449625580.

[PHIL-15] 1.0 ^1.1 ^1.2 ^1.3 ^1.4 ^1.5 "Public Health Image Library (PHIL)".

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Streptococcus pyogenes

Contents

Overview

Serotyping

Pathogenesis

Virulence factors

Diagnosis

Treatment

Antimicrobial therapy

Prophylaxis

References

Gallery

Other reading

References

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