Streptococcus pyogenes Quiz

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Questions and Answers

What is the Lancefield grouping of Streptococcus pyogenes?

Group A

What do Streptococcus pyogenes look like on a gram stain?

Gram positive cocci in chains/pairs

Are Group A strep encapsulated?

False (B)

What is the capsule of Group A strep made out of?

<p>Hyaluronic acid</p> Signup and view all the answers

Where can hyaluronic acid be found in the human body?

<p>connective tissue</p> Signup and view all the answers

Is the capsule of Strep pyogenes immunogenic?

<p>False (B)</p> Signup and view all the answers

What type of hemolysis does Group A Strep do?

<p>beta</p> Signup and view all the answers

What is the name of the skin infection caused by Group A strep that looks honey-crusted?

<p>impetigo</p> Signup and view all the answers

Which bacteria besides Group A strep can cause impetigo?

<p>Staphylococcus aureus</p> Signup and view all the answers

What is the clinical term for 'strep throat'?

<p>Pharyngitis</p> Signup and view all the answers

What is the most common cause of erysipelas?

<p>Group A strep</p> Signup and view all the answers

What is erysipelas?

<p>superficial cellulitis infection with well demarcated borders</p> Signup and view all the answers

What are the 3 pyrogenic infections caused by Strep pyogenes?

<p>impetigo, pharyngitis, erysipelas/cellulitis</p> Signup and view all the answers

Which exotoxin of Group A strep causes Scarlet fever?

<p>SpeA &amp; SpeC</p> Signup and view all the answers

What are the symptoms of Scarlet fever?

<p>reddening and swelling of the tongue, pharyngitis, widespread rash that spares the face</p> Signup and view all the answers

Which disease is associated with a strawberry tongue?

<p>Scarlet fever</p> Signup and view all the answers

Which 3 diseases are caused by the Streptococcal pyrogenic exotoxin (SPE)?

<p>scarlet fever, toxic shock-like syndrome (TSLS), necrotizing fasciitis</p> Signup and view all the answers

Which Group A strep toxin causes toxic shock-like syndrome?

<p>SpeA &amp; SpeC - superantigen</p> Signup and view all the answers

What is the name of the disease caused by Streptococcal pyrogenic exotoxin of Group A strep that is mediated by a superantigen?

<p>TSLS</p> Signup and view all the answers

Which of the diseases caused by Group A strep is a surgical emergency?

<p>necrotizing fasciitis</p> Signup and view all the answers

What does SpeB cause?

<p>necrotizing fasciitis</p> Signup and view all the answers

Which bacteria have the M protein?

<p>Group A strep</p> Signup and view all the answers

What is the main virulence factor of Group A strep that is responsible for rheumatic fever?

<p>M protein</p> Signup and view all the answers

How does the M protein work?

<p>Antiphagocytic: interferes with opsonization</p> Signup and view all the answers

Which virulence factor of Group A strep elicits a strong humoral response and creates an antibody against myosin?

<p>M protein</p> Signup and view all the answers

What is targeted by the antibodies made as a result of the M protein in Group A strep?

<p>myosin in heart</p> Signup and view all the answers

What is molecular mimicry?

<p>sequence similarities between foreign and self-peptides are sufficient to result in the cross-activation of autoreactive T or B cells by pathogen-derived peptides leads to autoimmunity</p> Signup and view all the answers

What does the M protein mimic?

<p>Myosin in heart</p> Signup and view all the answers

Which valve is most affected by rheumatic fever?

<p>mitral valve --&gt; mitral stenosis</p> Signup and view all the answers

Which bacteria cause rheumatic fever?

<p>Strep pyogenes</p> Signup and view all the answers

Can rheumatic fever start after Group A strep pharyngitis infections?

<p>False (B)</p> Signup and view all the answers

Can rheumatic fever start after Group A strep skin infections?

<p>False (B)</p> Signup and view all the answers

In which population is rheumatic fever commonly seen?

<p>young children - couldn't get strep pharyngitis treated because of access to health care</p> Signup and view all the answers

What are the 5 major symptoms of rheumatic fever?

<p>JONES: joints: polyarthritis, murmurs, pericarditis, myocarditis, subcutaneous nodules, erythema marginatum, Sydenham's chorea</p> Signup and view all the answers

How does rheumatic fever affect the heart?

<p>valvular damage --&gt; murmurs, pericarditis, myocarditis, endocarditis (pancarditis)</p> Signup and view all the answers

Which symptom of rheumatic fever entails involuntary movements of the hands and face?

<p>Sydenham's chorea</p> Signup and view all the answers

Which type of hypersensitivity is rheumatic fever?

<p>Type II</p> Signup and view all the answers

Which type of hypersensitivity reaction is Strep glomerulonephritis?

<p>Type III</p> Signup and view all the answers

What color of urine would you see in patients with glomerulonephritis?

<p>dark brown</p> Signup and view all the answers

Which bacteria can cause glomerulonephritis?

<p>Group A Strep</p> Signup and view all the answers

In glomerulonephritis, where do the circulating antibody-antigen immune complexes deposit?

<p>glomerulus</p> Signup and view all the answers

What happens to the face in glomerulonephritis?

<p>swelling - edema</p> Signup and view all the answers

What are the 2 main symptoms of glomerulonephritis?

<p>dark brown/cola-colored urine &amp; facial swelling</p> Signup and view all the answers

Can PSGN (post strep glomerulonephritis) occur after pharyngitis?

<p>False (B)</p> Signup and view all the answers

Can PSGN (post strep glomerulonephritis) occur after a superficial infection like impetigo?

<p>False (B)</p> Signup and view all the answers

Approximately how long after an initial strep infection does glomerulonephritis occur?

<p>2 weeks</p> Signup and view all the answers

Can early diagnosis and treatment of strep prevent rheumatic fever?

<p>False (B)</p> Signup and view all the answers

Can early diagnosis and treatment of strep prevent glomerulonephritis?

<p>False (B)</p> Signup and view all the answers

Which antibiotic is used to treat strep?

<p>penicillin</p> Signup and view all the answers

What does streptolysin do?

<p>beta hemolysis of blood</p> Signup and view all the answers

What does streptokinase do?

<p>converts plasminogen to plasmin (fibrinolytic)</p> Signup and view all the answers

When can streptokinase be given as a medicine?

<p>after MI or ischemic stroke to lyse clots</p> Signup and view all the answers

What does DNase do?

<p>depolymerizes DNA</p> Signup and view all the answers

List all the virulence factors of Group A Strep.

<p>SPE A, B, C; M protein; hyaluronic acid; streptolysin O; streptokinase; DNase</p> Signup and view all the answers

Is Group A strep bacitracin sensitive?

<p>False (B)</p> Signup and view all the answers

Is Group B strep bacitracin sensitive?

<p>False (B)</p> Signup and view all the answers

What does an antistreptolysin O (ASO) titer tell you?

<p>tells if you if the patient recently had a strep infection</p> Signup and view all the answers

Flashcards

Streptococcus pyogenes morphology

Gram-positive cocci in chains or pairs, often encapsulated with hyaluronic acid.

Lancefield grouping of S. pyogenes

Group A streptococci, classified based on their carbohydrate antigens.

Hyaluronic acid capsule in S. pyogenes

Found in human connective tissue, this capsule helps S. pyogenes evade the immune system by resembling a host component.

Beta hemolysis

A clear halo around the bacterial colony on blood agar, indicating the complete breakdown of red blood cells.

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Impetigo

A superficial skin infection characterized by honey-crusted lesions, often occurring alongside Staphylococcus aureus.

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Strep throat

Sore throat caused by S. pyogenes infection.

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Erysipelas

A superficial cellulitis infection with well-defined borders, commonly caused by S. pyogenes

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SpeA and SpeC

A type of exotoxin produced by S. pyogenes, responsible for scarlet fever.

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Scarlet fever rash

Rash characteristic of scarlet fever, sparing the face and accompanied by a reddened tongue.

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M protein

A major virulence factor of S. pyogenes, interfering with opsonization and leading to immune responses against heart muscle.

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Molecular mimicry

A situation where the immune system mistakenly targets the body's own tissues due to similarities with foreign antigens.

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Rheumatic fever

A post-streptococcal complication affecting the heart, often following untreated strep throat in children.

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JONES criteria for rheumatic fever

A mnemonic for remembering the symptoms of rheumatic fever.

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Polyarthritis in rheumatic fever

Inflammation of multiple joints, a hallmark of rheumatic fever.

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Heart involvement in rheumatic fever

Heart abnormalities like murmurs, pericarditis, and myocarditis, associated with rheumatic fever.

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Subcutaneous nodules in rheumatic fever

Nodules that appear on the limbs, a sign of rheumatic fever.

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Erythema marginatum in rheumatic fever

A rash with thick red borders, linked to rheumatic fever.

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Sydenham's chorea

Involuntary movements, particularly of the hands and face, associated with rheumatic fever.

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Type II hypersensitivity reaction

An immune response where antibodies attack self-antigens, often triggered by molecular mimicry.

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Post-streptococcal glomerulonephritis (PSGN)

A complication occurring after strep throat or skin infections, involving the kidneys.

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Immune complex deposition in PSGN

Immune complexes deposit in the glomeruli, triggering a Type III hypersensitivity reaction.

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Symptoms of PSGN

Dark brown urine and facial swelling are characteristic signs of PSGN.

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Prevention of rheumatic fever and PSGN

Early treatment of strep infections with penicillin is crucial to prevent rheumatic fever, but not PSGN.

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Penicillin for strep infections

A common first-line treatment for strep infections.

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Bacitracin

A substance that inhibits the growth of Group A streptococci, used to differentiate it from Group B streptococci.

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Streptolysin O

An enzyme produced by S. pyogenes, capable of degrading red blood cells.

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Streptokinase

An enzyme produced by S. pyogenes, used to break down clots and treat conditions like myocardial infarction.

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DNase in S. pyogenes

An enzyme produced by S. pyogenes, responsible for breaking down DNA.

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Antistreptolysin O (ASO) titer

A test measuring antibodies against streptolysin O, indicating recent strep infection.

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Study Notes

Streptococcus pyogenes Overview

  • Lancefield grouping: Group A
  • Appearance on Gram stain: Gram positive cocci in chains or pairs
  • Encapsulated with a capsule composed of hyaluronic acid, which is found in human connective tissue
  • Capsule is not immunogenic as hyaluronic acid is naturally present in the body

Hemolysis and Skin Infections

  • Exhibits beta hemolysis on blood agar
  • Causes impetigo, characterized by honey-crusted lesions, alongside Staphylococcus aureus
  • Leads to pharyngitis, commonly referred to as strep throat
  • Most common cause of erysipelas: a superficial cellulitis infection with defined borders

Pyrogenic Infections

  • Three main pyrogenic infections: impetigo, pharyngitis, and erysipelas/cellulitis
  • Scarlet fever caused by exotoxins SpeA and SpeC, presenting with a rash that spares the face and a reddened, swollen tongue (strawberry tongue)

Virulence Factors and Autoimmunity

  • M protein is a major virulence factor responsible for rheumatic fever; interferes with opsonization and elicits strong humoral responses, leading to antibodies against myosin in the heart
  • Molecular mimicry: similarity between foreign peptides and self-peptides can trigger autoimmune responses in rheumatic fever)

Rheumatic Fever Details

  • Common in young children with untreated strep pharyngitis
  • Symptoms summarized using JONES:
    • Joints: polyarthritis
    • Heart: murmurs, pericarditis, myocarditis (pancarditis)
    • Nodules: subcutaneous nodules on limbs
    • Erythema marginatum: rash with thick red borders
    • Sydenham's chorea: involuntary movements of hands and face
  • Type II hypersensitivity reaction

Glomerulonephritis (PSGN)

  • Occurs after pharyngitis or skin infections like impetigo, presenting with dark brown urine and facial edema
  • Immune complexes deposit in the glomerulus, causing Type III hypersensitivity reaction
  • Occurs approximately two weeks post-initial infection; early strep treatment prevents rheumatic fever but not glomerulonephritis

Treatment and Antibiotic Resistance

  • Initial treatment of strep infections typically involves penicillin
  • Group A strep sensitive to bacitracin; Group B strep is resistant
  • Streptolysin induces beta hemolysis; streptokinase converts plasminogen to plasmin, useful in treating myocardial infarction or ischemic stroke by lysing clots
  • DNase depolymerizes DNA

Summary of Key Virulence Factors

  • Key virulence factors include: SpeA, SpeB, SpeC, M protein, hyaluronic acid, streptolysin O, streptokinase, and DNase
  • Antistreptolysin O (ASO) titer used to determine recent strep infection

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