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Bacteriology > Streptococcus Pyogenes > Flashcards

Streptococcus Pyogenes Flashcards

1
Q

What is the major VF of Strep Pyogenes?

A

M protein

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2
Q

Characteristic of Strep. Pyogenes?

A
  • GABHS (group A beta hemolytic streptococci)
  • Gram positive cocci chain
  • major cause of cellulitis
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3
Q

Strep Pyogenes is most common cause of what?

A

Bacterial cause of sore throat and immune mediated complications

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4
Q

Transmission of Strep Pyogenes?

A

Person-to-person spread by respiratory droplets (pharyngitis) or through breaks in the skin after direct contact, fomite, or arthropod vector

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5
Q

What does the VF Hyaluronic acid capsule do?

A
  • produces C5a peptidase

- interferes with phagcytosis

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6
Q

What is the function of M protein?

A

hair like projections on CW which promotes adherence. Antiphagocytic and Anticomplement

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7
Q

What things are associated with Adherence and invasion into host cells?

A

Lipoteichoic acid, M protein, and F protein

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8
Q

Streptococcal Pyrogenic Exotoxins (erythrogenic toxin) are produced by?

A

Lysogenic strains of streptococci

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9
Q

Strep Pyrogenic Exotoxin acts as what and interacts with whom?

A

SPE acts as a superantigen and interacts with both macrophages and helper T cells.

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10
Q

Strep Pyrogenic Exotoxin is responsible for what?

A

Necrotizing fasciitis and streptococcal toxic shock syndrome as well as rash observed in patients with Scarlet Fever

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11
Q

Streptolysin S?

A

O2 stable –> non-immunogenic and responsible for the hemolysis in Blood agar

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12
Q

Streptolysin O?

A

O2 labile –> lyses WBC, platelets, RBC and mammalian cells. Immunogenic

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13
Q

what is the treatment of coronary artery disease and venous thromboses?

A

Streptokinase (fibrinolysin)

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14
Q

What is an important marker of S. pyogenes infection?

A

Antibodies against DNAse B

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15
Q

What are the Suppurative infections?

A
  • Phayngitis
  • Scarlet fever
  • Pyoderma
  • Erysipelas
  • Cellulitis
  • Necrotizing fasciitis
  • Strep toxic shock syndrome
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16
Q

What are the non-suppurative complications/sequelae?

A
  1. Acute rheumatic fever

2. Acute glomerulonephritis

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17
Q

Pharyngitis or ‘Strep Throat’ clinical features are?

A

Petachiae, Inflamed LN, Purulent exudate

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18
Q

Other signs of Pharyngitis ‘Strep throat’?

A
  • swollen “strawberry tongue”

- soft palate shows petachie

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19
Q

Scarlet fever is a complication of what?

A

Complication of pharyngitis due to pyrogenic toxin

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20
Q

Clinical manifestation of Scarlet fever RASH?

A

diffuse erythematous/sandpaper like rash on the upper chest and then spreads to the extremities with sparing of the mouth, palms and soles

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21
Q

Scarlet Fever clinical features?

A
  • Strawberry tongue
  • Pastia lines
  • Circumoral pallor (sparring of mouth)
  • Sandpaper wash
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22
Q

Impetigo effects what part of skin and soft tissue?

A

Epidermis

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23
Q

Erysipelas and Cellulitis effects what part of skin and soft tissue?

A

Dermis

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24
Q

Necrotizing fasciitis effects what part of skin and soft tissue?

A

Hypodermis

25
Q

What is Pyoderma/Impetigo?

A

Localized purulent streptococcal infection of skin that primarily effects exposed areas.

26
Q

What is the progression of pyoderma/impetigo?

A

Papule –> Vesicle –> Pustule –> Thick crust

27
Q

The fluid in blisters for Pyoderma/impetigo is…?

A

Serous or “honey colored”

28
Q

What is Erysipelas?

A

Acute inflammation of skin with lymphatic involvement. Often involves face, trunk and extremities following pharyngitis.

29
Q

Patients with Erysipelas usually experience what?

A

localized pain, inflammation, LM enlargement, and systemic signs.

30
Q

how do you distinguish cellulitis infected skin from non infected skin?

A

CAN NOT BE DISTINGUISHED it is not clear.

31
Q

What is Necrotizing fasciitis?

A

Streptococcal Gangrene

32
Q

Necrotizing fasciitis is caused by what factors of Strep pyogenes?

A

Hyaluronidase, M protein, and Hemolysin O and S

33
Q

Currently Strep. Pyogenes is most frequent agent of Necrotizing fasciitis. But what other organisms may cause this?

A
  • C. Perfringens

- S. Aureus

34
Q

How does Streptococcal Toxic Shock Syndrome (STTS) occur?

A

S. pyogenes grows in wound –> GABHS enters blood stream, and produce superantigen –> Fever, rash, shock, etc

35
Q

compared to STTS, how does TSS occur?

A

S. aureus grows in tampon or wound –> TSST-1 toxin enters bloodstream (no bacteremia) –> Fever, rash, shock.

36
Q

What are other infections of Strep pyogenes?

A
  1. Puerpural Sepsis “childbed fever”
  2. Acute Endocarditis
  3. Pneumonia
37
Q

What M types are rheumatogenic in Acute Rheumatic Fever (ARF)?

A

M6 and M12

38
Q

Acute Rheumatic Fever is due to…?

A

cross-reactions between antigens of the heart and joint tissues, and the streptococcal antigen

39
Q

Acute Post-Streptococcal Glomerulonephritis characteristics?

A
  • Follows Skin or Throat infections
  • Presumptive: Dark urine (hematuria)
  • Definitive
40
Q

Acute Post-Streptococcal Glomerulonephritis Key finding?

A

Loss of bowman’s space, choking or vessel lumen

41
Q

Importance of Microscopic examination of smears?

A

Gram +ve cocci in chains seen in the pus are important, but in throat swab it is not important.

42
Q

What is the selective medium for Strep. pyogenes?

A

Crystal Violet Blood Agar

43
Q

When you do a culture on blood agar what do you see?

A

Small, circular, colonies with wide zone of B haemolysis.

44
Q

Catalase test for Streptococci would show what result?

A

Negative

45
Q

PYR test (pyrrolidonyl naphthalamide) would yield what result for Strep pyogenes?

A

Positive for Strep. Pyogenes BUT, negative for other streptococci

46
Q

Bacitracin sensitivity would yield what result for Strep pyogenes?

A

Positive for Strep pyogenes BUT, negative for other streptococci

47
Q

Serological test would provide what?

A

evidence for prior streptococcal infection as Abs appear after 3-4 weeks.

48
Q

What is are some examples of a serological test for Streptococci?

A
  • Antistreptolysin O (ASO) test (neutralisation test)
  • Antigen Detection Test
  • Rapid Latex Antigen Kit
49
Q

What is Antigen detection test used for?

A

its a agglutination test used to see group A streptococcal antigen from throat swab.

50
Q

What is the treatment for Strep Pyogenes?

A

Penicillin is drug of choice.

  • starting therapy within 10 days prevents rheumatic fever
  • no treatment for glomerulonephritis
51
Q

Children 5-15 years old can get what with s. pneumoniae?

A

Pharyngitis

52
Q

Children ages 2-5 with poor personal hygiene can get what from s. pneumoniae?

A

Pyoderma

53
Q

What is useful for documenting recent group A streptococcal infections?

A

Anti-ASO test

54
Q

What is the criteria to diagnose rheumatic fever?

A

“JONES”

  • Joints: polyarthritis
  • Carditis
  • Nodules (subcutaneous)
  • Erythema marginatum
  • Syndenham’s chorea
55
Q

Pharyngitis can result in what?

A

rheumatic fever and glomerulonephritis

56
Q

Impetigo more commonly precedes what?

A

glomerulonephritis more than pharyngitis

57
Q

ASO titer detects recent infection with what?

A

S. pyogenes

58
Q

Strep Pyogenes causes? (Pyogenic, Toxogenic, Immunogenic)

A

Pyogenic: pharyngitis, cellulitis, impetigo

Toxogenic: scarlet fever, toxic-shock like syndrome, necrotizing fasciitis

Immunogenic: rheumatoid arthritis, acute glomerulonephritis

Bacteriology (17 decks)

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