Streptococcus pyogenes: Difference between revisions
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Streptococcus pyogenes
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* Also commonly referred to as '''Group A Streptococcus''' |
* Also commonly referred to as '''Group A Streptococcus''' |
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== Background == |
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=== Microbiology === |
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* [[Has Gram stain::Gram-positive]] coccus, typically in short chains |
* [[Has Gram stain::Gram-positive]] coccus, typically in short chains |
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* Non-motile, non–spore forming, catalase-negative, and facultatively anaerobic |
* Non-motile, non–spore forming, catalase-negative, and facultatively anaerobic |
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* [[Has hemolysis pattern::β hemolytic]] on blood agar (complete hemolysis) |
* [[Has hemolysis pattern::β hemolytic]] on blood agar (complete hemolysis) |
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* Can be distinguished from other β-hemolytic streptococci by its susceptibility to [[bacitracin]] |
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== Pathophysiology == |
=== Pathophysiology === |
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* Capsular '''hyaluronic acid''' is similar to human |
* Capsular '''hyaluronic acid''' is similar to human |
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* '''M protein''' is the main factor imparting virulence |
* '''M protein''' is the main factor imparting virulence |
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* '''DNAse''' (streptokinase) disrupts coagulation and the body's ability to prevent the bacteria from spreading |
* '''DNAse''' (streptokinase) disrupts coagulation and the body's ability to prevent the bacteria from spreading |
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=== Antibiotic resistance === |
==== Antibiotic resistance ==== |
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* The PBP is extremely stable, so low mutation rate, and essentially always susceptible to penicillin |
* The PBP is extremely stable, so low mutation rate, and essentially always susceptible to penicillin |
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* Macrolides |
* Macrolides |
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== Clinical Presentation == |
== Clinical Presentation == |
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* Asymptomatic carriage |
* Asymptomatic carriage |
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* Streptococcal [[pharyngitis]] |
* Streptococcal [[pharyngitis]] |
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== Classification of Invasive Disease == |
== Classification of Invasive Disease == |
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* As per the Public Health Agency of Canada [https://www.canada.ca/en/public-health/services/diseases/group-a-streptococcal-diseases/health-professionals/national-case-definition.html National case definition: Invasive group A streptococcal disease] |
* As per the Public Health Agency of Canada [https://www.canada.ca/en/public-health/services/diseases/group-a-streptococcal-diseases/health-professionals/national-case-definition.html National case definition: Invasive group A streptococcal disease] |
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=== Confirmed case === |
=== Confirmed case === |
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* '''Laboratory confirmation''' of infection with or without clinical evidence of invasive disease, requiring isolation of group A streptococcus (''Streptococcus pyogenes'') from a normally sterile site |
* '''Laboratory confirmation''' of infection with or without clinical evidence of invasive disease, requiring isolation of group A streptococcus (''Streptococcus pyogenes'') from a normally sterile site |
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** Blood, CSF, pleural fluid, pericardial fluid, peritoneal fluid, deep tissue specimen taken during surgery (e.g. muscle collected during debridement for necrotizing fasciitis), bone or joint fluid excluding the middle ear and superficial wound aspirates (e.g. skin and soft tissue abscesses). |
** Blood, CSF, pleural fluid, pericardial fluid, peritoneal fluid, deep tissue specimen taken during surgery (e.g. muscle collected during debridement for necrotizing fasciitis), bone or joint fluid excluding the middle ear and superficial wound aspirates (e.g. skin and soft tissue abscesses). |
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=== Probable case === |
=== Probable case === |
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* '''Clinical evidence''' of invasive disease in the absence of another identified aetiology and with non-confirmatory laboratory evidence of infection: |
* '''Clinical evidence''' of invasive disease in the absence of another identified aetiology and with non-confirmatory laboratory evidence of infection: |
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** Isolation of group A streptococcus from a non-sterile site |
** Isolation of group A streptococcus from a non-sterile site |
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=== Clinical evidence === |
=== Clinical evidence === |
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* Streptococcal toxic shock syndrome, which is characterized by hypotension (systolic blood pressure ≤ 90 mm Hg in an adult and < 5 percentile for age for children) and at least two of the following signs: |
* Streptococcal toxic shock syndrome, which is characterized by hypotension (systolic blood pressure ≤ 90 mm Hg in an adult and < 5 percentile for age for children) and at least two of the following signs: |
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* Renal impairment (creatinine level ≥ 177 μmol/L for adults) |
* Renal impairment (creatinine level ≥ 177 μmol/L for adults) |
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== Prognosis == |
== Prognosis == |
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* Highest risk of streptococcal [[toxic shock syndrome]] (TSS) or death |
* Highest risk of streptococcal [[toxic shock syndrome]] (TSS) or death |
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** [[Necrotizing fasciitis]] (50% and 50%) |
** [[Necrotizing fasciitis]] (50% and 50%) |
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Revision as of 00:59, 30 April 2020
- Also commonly referred to as Group A Streptococcus
Background
Microbiology
- Gram-positive coccus, typically in short chains
- Non-motile, non–spore forming, catalase-negative, and facultatively anaerobic
- β hemolytic on blood agar (complete hemolysis)
- Can be distinguished from other β-hemolytic streptococci by its susceptibility to bacitracin
Pathophysiology
Virulence factors
- Capsular hyaluronic acid is similar to human
- M protein is the main factor imparting virulence
- M protein differences given S. pyogenes its serotypes (about 150)
- Confers resistance to phagocytosis by modulating host immune response
- Impairs granulocyte maturation even if it is phagocytosed
- It is also an adhesin
- F protein binds to fibronectin, helps with adhesion
- Hemolysins, include streptolysin O and S, confers red and white cell lysis
- O means oxygen-labile, so will only grow in anaerobic environment, while S is stable in oxygen
- DNAse (streptokinase) disrupts coagulation and the body's ability to prevent the bacteria from spreading
Antibiotic resistance
- The PBP is extremely stable, so low mutation rate, and essentially always susceptible to penicillin
- Macrolides
- Inducible in the presence of erythromycin (D test)
- Efflux pump
Clinical Presentation
- Asymptomatic carriage
- Streptococcal pharyngitis
- Scarlet fever
- Skin and soft tissue infections, including cellulitis, erysipelas, impetigo, and necrotizing fasciitis
- Upper and lower respiratory tract infections
- Bacteremia without a focus
- Septic arthritis and osteomyelitis
- Myositis
- Pelvic infections, including postpartum endometritis (puerperal fever)
- Streptococcal toxic shock syndrome
- Less commonly:
- Pneumonia, typically post-viral and associated with military recruits, and often complicated by empyema and 38% mortality
- Lymphangitis
- Meningitis
- Endocarditis
- Sudden unexplained death in an otherwise healthy person
- Post-infectious syndromes
Classification of Invasive Disease
- As per the Public Health Agency of Canada National case definition: Invasive group A streptococcal disease
Confirmed case
- Laboratory confirmation of infection with or without clinical evidence of invasive disease, requiring isolation of group A streptococcus (Streptococcus pyogenes) from a normally sterile site
- Blood, CSF, pleural fluid, pericardial fluid, peritoneal fluid, deep tissue specimen taken during surgery (e.g. muscle collected during debridement for necrotizing fasciitis), bone or joint fluid excluding the middle ear and superficial wound aspirates (e.g. skin and soft tissue abscesses).
Probable case
- Clinical evidence of invasive disease in the absence of another identified aetiology and with non-confirmatory laboratory evidence of infection:
- Isolation of group A streptococcus from a non-sterile site
- or
- Positive group A streptococcus antigen detection
Clinical evidence
- Streptococcal toxic shock syndrome, which is characterized by hypotension (systolic blood pressure ≤ 90 mm Hg in an adult and < 5 percentile for age for children) and at least two of the following signs:
- Renal impairment (creatinine level ≥ 177 μmol/L for adults)
- Coagulopathy (platelet count ≤ 100,000/mm3 or disseminated intravascular coagulation)
- Liver function abnormality (SGOT, SGPT, or total bilirubin ≥ 2x upper limit of normal)
- Adult respiratory distress syndrome
- Generalized erythematous macular rash that may desquamate
- Soft-tissue necrosis, including necrotizing fasciitis, myositis or gangrene
- Meningitis
Prognosis
- Highest risk of streptococcal toxic shock syndrome (TSS) or death
- Necrotizing fasciitis (50% and 50%)
- Pneumonia (30% and 30%)
- Bacteremia (15% and 25%)
References
- ^ Athanasios G. Michos, Chrysanthi G. Bakoula, Maria Braoudaki, Foteini I. Koutouzi, Eleftheria S. Roma, Anastasia Pangalis, Georgia Nikolopoulou, Elena Kirikou, Vassiliki P. Syriopoulou. Macrolide resistance in Streptococcus pyogenes: prevalence, resistance determinants, and emm types. Diagnostic Microbiology and Infectious Disease. 2009;64(3):295-299. doi:10.1016/j.diagmicrobio.2009.03.004.
