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

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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

  • 1. Streptococcus pyogenes tonsilitis[14]
  • Preferred regimen (1): Penicillin V 250 mg PO bid or tid (for children) 250 mg PO qid or 500 mg PO bid (for adults) for 10 days[15]
  • Preferred regimen (2): Benzathine penicillin G if < 27kg: 600,000 U, if > 27kg 1,200,000 U IM single-dose[16]
  • Alternative regimen (1): Amoxicillin 50 mg/kg/day PO qd for 10 days OR 25 mg/kg/day PO bid for 10 days. Its oral suspension is more tolerable to children and it is better absorbed by the GI tract[17]
  • Alternative regimen (2): first generation Cephalosporins are acceptable for treating recurrent group A streptococcus infection but not as first-line therapy[18][16]
  • Alternative regimen (3): Clarithromycin 250 mg PO bid for 10 days OR Azithromycin 12 mg/kg maximum 500 mg PO on day 1 THEN 6 mg/kg maximum 250 mg PO qd on days 2 through 5 OR Erythromycin 20 mg/kg/day PO or 40 mg/kg/day (ethylsuccinate) PO bid for 10 days.
  • Alternative regimen (4): Clindamycin for penicillin-intolerant patients with erythromycin-resistant strains.
  • Note: Intramuscular penicillin is the only therapy that has been shown to prevent initial attacks of rheumatic fever in controlled studies[19]
  • 2. Recurrent Streptococcus pyogenes tonsilitis[20]
  • Preferred regimen (1): Clindamycin 20-30 mg/kg/day PO tid (for children), 600 mg/day bid, tid or qid (for adults) for 10 days
  • Preferred regimen (2): Amoxicillin-clavulanic acid 40 mg/kg/day PO tid (for children), 500 mg bid (for adults) for 10 days
  • Alternative regimen: Benzathine penicillin G if <27kg: 600,000 U, if >27kg 1,200,000 U IM single-dose ± Rifampin 20 mg/kg/day PO bid for 4 days
  • 3. Secondary prophylaxis for rheumatic fever[16]
  • Preferred regimen (1): Benzathine penicillin G if <27kg: 600,000 U, if >27kg 1,200,000 U IM every 4 weeks
  • Alternative regimen (1): Penicillin V potassium 250 mg PO bid
  • Alternative regimen (2): Sulfadiazine if <27kg 0.5 g PO qd, if >27kg 1 g PO qd
  • Duration of treatment: if residual cardiac disease, keep treatment until 40 patient is 40 years old or for 10 years (whichever is longer); if there's no residual cardiac disease keep treatment for 10 years or until age 21 years (whichever is longer); if there's rheumatic fever without carditis keep it for 5 years or until age 21 years (whichever is longer).
  • Note: For patients allergic to penicillin and sulfadiazine, consider a macrolide or azalide antibiotic
  • 4. Streptococcus pyogenes bacteremia[21]
  • Preferred regimen: Penicillin G 4 million units IV q4h AND Clindamycin 900 mg IV q8h for at least 14 days
  • Penicillin is added to the regimen to cover any other group A streptococcus which might be resistant to Clindamycin.
  • Alternative regimen (1): Erythromycin
  • Alternative regimen (2): Azithromycin
  • Alternative regimen (3): Clarithromycin
  • Alternative regimen (4): any other β-lactam[22]
  • Note (1): Macrolide resistance is increasing.
  • Note (2): Consider using intravenous immune globulin in patients with invasive infection and signs of shock. Immunoglobulin-G IV 1 g/kg day 1, then 0.5 g/kg days 2 & 3.
  • Note (3): If shock, administer massive IV fluids (10-20 L/day), Albumin if <2 g/dL, debridement of necrotic tissue.
  • 5. Streptococcus pyogenes celulitis
  • Preferred regimen: treat as Streptococcus pyogenes bacteremia
  • 6 Epiglottitis in childern[23]
  • Preferred regimen (1): Cefotaxime 50 mg/kg IV q8h
  • Preferred regimen (2): Ceftriaxone 50 mg/kg IV q24h
  • Alternative regimen (1): Amoxicillin-SB 100–200 mg/kg qd q6h
  • Alternative regimen (2): Trimethoprim-Sulfamethoxazole 8–12 mg/kg bid
  • Note: Have tracheostomy set “at bedside.” Chloro is effective, but potentially less toxic alternative agents available.
  • 7 Burn wound sepsis[24]
  • Note: For necrotizing fasciitis, surgical consultation for emergent fasciotomy and debridement; repeat debridements usually necessary.
  • Note: For myositis-debirdement is recommended.
  • 10.1 Keratitis
  • 10.1.1 Acute bacterial keratitis
  • Preferred regimen: Moxifloxacin eye gtts. 1 gtt tid for 7 days
  • Alternative therapy: Gatifloxacin eye gtts. 1-2 gtts q2h while awake for 2 days, then q4h for 3-7 days.
  • Note: Prefer Moxifloxacin due to enhanced lipophilicity and penetration into aqueous humor (1 gtt = 1 drop).
  • 10.1.2 Keratitis due to dry cornea, diabetes, immunosuppression
  • Preferred regimen: Cefazolin (50 mg/mL) AND (Gentamicin OR Tobramycin (14 mg/mL) q15–60 min around clock for 24–72 hrs, then slow reduction)
  • Alternative therapy: Vancomycin (50 mg/mL) AND Ceftazidime (50 mg/mL) q15–60 min around clock for 24–72 hrs, then slow reduction.
  • Note: Specific therapy guided by results of alginate swab culture and sensitivity. Ciprofloxacin 0.3% found clinically equivalent to CefazolinAND Tobramycin; only concern was efficacy of Ciprofloxacin vs S. pneumoniae
  • 10.2 Dacryocystitis (lacrimal sac)
  • 11. Suppurative phlebitis[28]
  • Preferred regimen: Vancomycin 15 mg/kg IV q12h (normal weight)
  • Alternative regimen: Daptomycin 6 mg/kg IV q12h
  • Note: Retrospective study for suppurative phlebitis recommends 2-3 weeks IV therapy and 2 weeks PO therapy.
  • 12. Infected prosthetic joint[29]
  • Preferred regimen: Penicillin G 2 million units IV q4h OR Ceftriaxone 2 g IV q24h for 4 weeks
  • Note: Debridement & prosthesis retention with intravenous antibiotics.
  • 13. “Hot” tender parotid swelling[30]
  • Preferred regimen: Nafcillin OR Oxacillin 2 g IV q4h
  • Note: Predisposing factors are stone(s) in Stensen’s duct, dehydration. Therapy depends on ID of specific etiologic organism.
  • 14. Diabetic foot ulcer (ulcer with <2 cm of superficial inflammation)[31]
  • 15. Recurrent cellulitis, chronic lymphedema prophylaxis[32]

Prophylaxis

  • Steptococcus Pyogenes (groups A Streptococcus) prophylaxis [33]
  • Acute rheumatic fever prophylaxis
  • Recurrent cellulitis, chronic lymphedema prophylaxis

References

  1. Ryan KJ; Ray CG (editors) (2004). Sherris Medical Microbiology (4th ed. ed.). McGraw Hill. ISBN 0-8385-8529-9. 
  2. Lancefield RC (1928). "The antigenic complex of Streptococcus hemolyticus". J Exp Med. 47: 9–10. 
  3. Lancefield RC, Dole VP (1946). "The properties of T antigen extracted from group A hemolytic streptococci". J Exp Med. 84: 449–71. 
  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. 
  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. 
  6. Bisno AL, Brito MO, Collins CM (2003). "Molecular basis of group A streptococcal virulence". Lancet Infect Dis. 3 (4): 191–200. PubMed. 
  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. 
  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. 
  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. 
  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. 
  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. 
  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): 681–4. PMID 3903089. 
  14. Betriu C, Sanchez A, Gomez M, Cruceyra A, Picazo JJ (1993). "Antibiotic susceptibility of group A streptococci: a 6-year follow-up study.". Antimicrob Agents Chemother. 37 (8): 1717–9. PMC 188051Freely accessible. PMID 8215292. 
  15. Gerber MA, Baltimore RS, Eaton CB, Gewitz M, Rowley AH, Shulman ST; et al. (2009). "Prevention of rheumatic fever and diagnosis and treatment of acute Streptococcal pharyngitis: a scientific statement from the American Heart Association Rheumatic Fever, Endocarditis, and Kawasaki Disease Committee of the Council on Cardiovascular Disease in the Young, the Interdisciplinary Council on Functional Genomics and Translational Biology, and the Interdisciplinary Council on Quality of Care and Outcomes Research: endorsed by the American Academy of Pediatrics.". Circulation. 119 (11): 1541–51. PMID 19246689. doi:10.1161/CIRCULATIONAHA.109.191959. 
  16. 16.0 16.1 16.2 Shulman ST, Bisno AL, Clegg HW, Gerber MA, Kaplan EL, Lee G; et al. (2012). "Clinical practice guideline for the diagnosis and management of group A streptococcal pharyngitis: 2012 update by the Infectious Diseases Society of America.". Clin Infect Dis. 55 (10): 1279–82. PMID 23091044. doi:10.1093/cid/cis847. 
  17. Curtin-Wirt C, Casey JR, Murray PC, Cleary CT, Hoeger WJ, Marsocci SM; et al. (2003). "Efficacy of penicillin vs. amoxicillin in children with group A beta hemolytic streptococcal tonsillopharyngitis.". Clin Pediatr (Phila). 42 (3): 219–25. PMID 12739920. 
  18. Pichichero ME (2005). "A review of evidence supporting the American Academy of Pediatrics recommendation for prescribing cephalosporin antibiotics for penicillin-allergic patients.". Pediatrics. 115 (4): 1048–57. PMID 15805383. doi:10.1542/peds.2004-1276. 
  19. WANNAMAKER LW, RAMMELKAMP CH, DENNY FW, BRINK WR, HOUSER HB, HAHN EO; et al. (1951). "Prophylaxis of acute rheumatic fever by treatment of the preceding streptococcal infection with various amounts of depot penicillin.". Am J Med. 10 (6): 673–95. PMID 14837911. 
  20. Bisno AL, Gerber MA, Gwaltney JM, Kaplan EL, Schwartz RH, Infectious Diseases Society of America (2002). "Practice guidelines for the diagnosis and management of group A streptococcal pharyngitis. Infectious Diseases Society of America.". Clin Infect Dis. 35 (2): 113–25. PMID 12087516. doi:10.1086/340949. 
  21. Gilbert, David (2015). The Sanford guide to antimicrobial therapy. Sperryville, Va: Antimicrobial Therapy. ISBN 978-1930808843. 
  22. Gilbert, David (2015). The Sanford guide to antimicrobial therapy. Sperryville, Va: Antimicrobial Therapy. ISBN 978-1930808843. 
  23. Bartlett, John (2012). Johns Hopkins ABX guide : diagnosis and treatment of infectious diseases. Burlington, MA: Jones and Bartlett Learning. ISBN 978-1449625580. 
  24. Bartlett, John (2012). Johns Hopkins ABX guide : diagnosis and treatment of infectious diseases. Burlington, MA: Jones and Bartlett Learning. ISBN 978-1449625580. 
  25. Bartlett, John (2012). Johns Hopkins ABX guide : diagnosis and treatment of infectious diseases. Burlington, MA: Jones and Bartlett Learning. ISBN 978-1449625580. 
  26. Bartlett, John (2012). Johns Hopkins ABX guide : diagnosis and treatment of infectious diseases. Burlington, MA: Jones and Bartlett Learning. ISBN 978-1449625580. 
  27. Bartlett, John (2012). Johns Hopkins ABX guide : diagnosis and treatment of infectious diseases. Burlington, MA: Jones and Bartlett Learning. ISBN 978-1449625580. 
  28. Bartlett, John (2012). Johns Hopkins ABX guide : diagnosis and treatment of infectious diseases. Burlington, MA: Jones and Bartlett Learning. ISBN 978-1449625580. 
  29. Bartlett, John (2012). Johns Hopkins ABX guide : diagnosis and treatment of infectious diseases. Burlington, MA: Jones and Bartlett Learning. ISBN 978-1449625580. 
  30. Bartlett, John (2012). Johns Hopkins ABX guide : diagnosis and treatment of infectious diseases. Burlington, MA: Jones and Bartlett Learning. ISBN 978-1449625580. 
  31. Bartlett, John (2012). Johns Hopkins ABX guide : diagnosis and treatment of infectious diseases. Burlington, MA: Jones and Bartlett Learning. ISBN 978-1449625580. 
  32. Bartlett, John (2012). Johns Hopkins ABX guide : diagnosis and treatment of infectious diseases. Burlington, MA: Jones and Bartlett Learning. ISBN 978-1449625580. 
  33. Bartlett, John (2012). Johns Hopkins ABX guide : diagnosis and treatment of infectious diseases. Burlington, MA: Jones and Bartlett Learning. ISBN 978-1449625580. 

Gallery


Other reading

  • Gladwin, Mark and Bill Trattler. Clinical Microbiology Made Ridiculously Simple, 3rd edition, 2004.
  • Brooks, Geo F., Janet S. Butel, and Stephen A. Morse. Jawetz, Melnick, and Adelberg's Medical Microbiology, 22nd edition, 2001.



References


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