(VI) Gram Positive Cocci (5)*Streptococcus pyogenes (GAS) Flashcards
Hemolysis: Strep. pyogenes
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What organism has a capsule made of hyaluronic acid?
Strep. pyogenes
What type of infections does Strep. pyogenes cause?
(1) Pharyngitis/tonsillitis
(2) Impetigo
(3) Cellulitis/Erysipelas
Name 3 signs/symptoms of Scarlett fever
(1) “Strawberry tongue”
(2) Pharyngitis
(3) Diffuse rash sparing the face
Name 2 effects of Strep. pyogenes’ M protein
(1) Anti-phagocytic
(2) ⇒ Abs against mitral valve
Which of Strep. pyogenes’ exotoxins causes necrotizing fasciitis?
SpeB
(“B for Burnt”)
Which of Strep. pyogenes’ exotoxins are superantigens?
(1) SpeA
(2) SpeC
What type of Strep. pyogenes infection precipitates rheumatic fever?
Pharyngitis
What does the JONES criteria stand for?
(1)** J**oints (Polyarthritis)
(2) ♥ - Rheumatic Heart Disease
(3) Nodules
(4) Erythema marginatum
(5) Syndenham’s chorea
What type of Strep. pyogenes infection precipitates post-streptococcal glomerulonephritis?
(1) Pharyngitis
(2) Skin infections
How long does it take for post-streptococcal glomerulonephritis to develop?
~2 weeks
(Contrast with IgA nephropathy which occurs at same time as the pharyngitis)
Which sequelae of a Strep. pyogenes infection is NOT prevented by treatment?
Post-streptococcal glomerulonephritis
(He’s holding the penicillin ∴ being treated, yet he still has facial edema/puffiness. Treatment prevents rheumatic fever)
Name 5 virulence factors of Strep. pyogenes
(1) Hyaluronidase
(2) Streptolysin O
(3) Streptokinase
(4) DNAse
(5) SpeA-C
How can you differentate GAS from GBS?
GAS is Bacitracin sensitive
What lab test can be ordered to check for recent Strep. pyogenes infection?
ASO titer
Desribe the rash of Scarlett fever
Diffuse but spares the face
How are streptococci spp categorized?
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How are streptococci spp categorized?
***Hemolysis (Alpha complete, Beta partial, Gamma non) and cell wall Lancefield antigens
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Alpha Hemolytic = partially lyse RBC = greenish discolouration –> Strep Pneumoniae, Viridans Streps
Beta Hemolytic = fully lyse RBC = clear zone (GAS, GBS, GDS/enterococcus) (and Staph aureus)
Lancefield antigens gives the grouping names
Grp A Strep = Strep pyogenes
Grp B Strep = Strep agalatiae
Grp D strep = Enterococcus Spp
Strep Pneumo and Viridans Streps are alpha hemolytic, don’t care about lancefield antigens (IN GENERAL LA. ik got long story but not impt)
How to diagnose Strep Pyogenes? (IMPT!!!)
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How to diagnose Strep Pyogenes? (IMPT!!!)
ASO titre, antibodies to hyaluronidase or DNAse B
ASO = Anti-Streptolysin O
What are the common clinical presentations of streptococcus pyogenes infection? (IMPT!!!)
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What are the common clinical presentations of streptococcus pyogenes infection? (IMPT!!!)
- Pharyngitis/tonsillitis (local complications: peritonsillar abscess (quinsy), sinusitis, otitis media, mastoiditis, post viral pneumonia)
- Skin & soft tissue infections: Impetigo (restricted to epidermis), erysipelas (palpable border), cellulitis (not distinct border), wound infections
- Exotoxin mediated **Scarlet fever, Streptococcal TSS (toxic shock like syndrome), Necrotizing fascilitis **
- Non-suppurative complications (delayed ab-mediated disesease): Acute Rheumatic Ferver (ARF), Acute GlomeruloNephritis (AGN)
Strep Pyogenes is almost a buzzword for ARF!! Superimpt.
Pathogenesis of ARF is molecular mimicry (cross-reactivity). M proteins from S pyogenes is similar to heart myosin protein –> rheumatic heart disease, predisposes to subacute bacterial endocarditis
What are the virulence factors of Streptococcus Pyogenes? (6) (IMPT!!!)
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What are the virulence factors of Streptococcus Pyogenes? (6) (IMPT!!!)
- **Streptolysin O **& S (responsible for hemolysis, damages leukocytes)
- M protein (Inhibits complement activation and phagocytosis, but immune system produces specific opsonic antibodies to it)
- Streptococcal Pyrogenic Exotoxins (causes fever, scarlet fever,TSS)
- Hyaluronidase (breaks down intercellular cement, allows for spread through tissues)
- DNase
- Streptokinase
Anti-Streptolysin O (ASO) titre and Antibody to Hyaluronidase is diagnostic!!
M Protein for molecular mimicry in acute rheumatic fever
Btw pyogenes = “pus-producing”
What is the revised Jones criteria for ARF?
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N - […]
E - […]
S - […]
What is the revised Jones criteria for ARF?
J - Joints (Polyarthritis)
♥ - Rheumatic Heart Disease
N - Nodules
E - Erythema Marginatum
S - Syndenham’s Chorea
These are major criterias. minor criterias include fever, arthralgia, elevated acute phase reactants (ESR,CRP), prolonged PR interval
What is the treatment for Strep. Pyogenes infection?
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What about necrotising fasciitis?
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What is the treatment for Strep. Pyogenes infection?
Penicillin
What about necrotising fasciitis?
Penicillin + Clindamycin (inhibit toxin synthesis), debridement (THIS IS SURGICAL), IVIG
