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Microbiology Block 2 > Strep Pyogenes > Flashcards

Strep Pyogenes Flashcards

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1
Q

what are the group A streptococci?

A

strep pyogenes

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2
Q

is streptococcus catalase + or -?

A

it is catalase negative

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3
Q

will strep pyogenes be sensitive or resistant to bacitracin?

A

it will be sensitive

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4
Q

what are the 3 virulence factors for strep pyogenes?

A

M protein *

Streptolyin O*, streptolysin S

Streptococcal pyrogenic exotoxins (SPEs)

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5
Q

if cultivated on blood agar, it will cause what hemolysis?

A

beta-hemolytic

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6
Q

what does the M protein in strep pyogenes do?

A
  • Mediates adherence to host cell
  • Facilitates invasion of host cell
  • Anti-phagocytic
    • blocks binding of complement C3 to bacterial cell wall preventing phagocytosis
    • Binds Fc portion of opsonizing antibodies preventing phagocytosis
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7
Q

what does Streptolysin O * do?

A
  • Lyses RBCs, leukocytes, platelets
  • It is Antigenic (stimulates antibody production)
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8
Q

how can streptolysin O be detected?

A

using ASO

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9
Q

what do streptokinases do?

A
  • causes Lysis of clots and fibrin deposits *
  • Facilitates spread of infection
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10
Q

what does C5a peptidase * do?

A

Degrades C5a  reduced complement-mediated inflammation

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11
Q

what do the Streptococcal pyrogenic exotoxins (SPEs)* do?

A
  • Cause the rash of scarlet fever
  • Produced by Streptococcal TSS strains
  • can be Superantigen *
    • Interacts with both macrophages & T cells causing non-specific activation of T cells
    • This results in release of large amts of cytokines (IL-1, IL-2 TNF-α)
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12
Q

what diseases does strep pyogenes cause?

A

phrayngitis (Strep Throat)

scarlet fever

skin and soft tissue infections

strep toxic shock syndrome

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13
Q

what is the most common cause of bacterial pharyngitis?

A

strep pyogenes

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14
Q

how is phrayngitis (strep throat) diagnosed?

how is the diagnosis confirmed?

A

rapid strep antigen test

confirmed on culture

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15
Q

can strep throat be left untreated and self-resolves? WHY?

A

NO! must treat with antibiotics

if left untreated may lead to rheumatic fever

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16
Q

what is this?

A

strep throat

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17
Q

what is this?

A

strep throat

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18
Q

what 2 complications can result from strep throat (strep pharyngits)?

A

Rheumatic fever and Scarlet Fever

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19
Q

what will cause the scarlet fever complication?

A

Group A strep producing pyrogenic exotoxin from strep pyogenes

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20
Q

how does scarlet fever present to in a clinic?

A

Erythematous rash *that starts in upper chest and spreads to extremeties

strawberry tongue

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21
Q

what is this?

what is this a consequence of?

who causes this?

A

erythemathous rash

scarlet fever

strep pyogenes

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22
Q

what is this?

A

strawberry tongue in scarlet fever

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23
Q

what skin and soft tissue infections does strep pyogenes cause?

A

impetigo

cellulatis

erysipelas

necrotizing fasciitis

24
Q

what is this?

A

impetigo

25
Q

impetigo looks like what other infection?

A

staph aureus

26
Q

impetigo infection lesion is described as what?

A

honey-crusted lesions

27
Q

what is erysipelas?

A

acute inflammation of the deep dermis and upper subcutis by strep

28
Q

does erysipelas spread?

A

yes

29
Q

what is the presentation for erysipelas?

A

lesions that present as hot, painful, red, raised

30
Q

what will erysipelas lead to if left untreated?

A

respiratory tract or skin infection

31
Q

what is this?

A

erysipelas

32
Q

what is cellulitis?

what differentiates cellulitis from erysipelas?

A

Deeper infection than erysipelas

No clearly demarked separation between normal and infected skin

33
Q

what is necrotizing fasciitis?

A

Bacteria spreads along superficial and deep fascial planes and enters following minor trauma, or hematogenous spread from Group A Strep throat infection to site of blunt trauma/muscle strain

34
Q

what will necrotizing fasciitis cause?

A

extensive destruction of muscle and fat *

35
Q

what is a major risk factor to developing necrotizing fasciitis?

A

History of recent varicella-zoster virus (VZV) infection

36
Q

what is this?

A

necrotizing fasciitis

37
Q

what strains of streptococci will cause strep toxic shock syndrome?

A
  • prominent capsule and SPEs (pyrogenic exotoxin - superantigen) *
  • M1 and M3 serotypes
  • Preceding skin infection (eg cellulitis)
38
Q

what will differentiate strep toxic shock syndrome from staph toxic shock syndrome?

A

Blood cultures positive for Strep pyogenes*, the bacteria will in the blood (bacteremia)

39
Q

strep bacteremia usually follows what 2 diseases?

A

necrotizing fasciitis or toxic shock syndrome

40
Q

what are the Non-suppurative Post-streptococcal sequelae? (complication from giving antibiotics)

A

Rheumatic fever

Acute glomerulonephritis

41
Q

how do you diagnose rheumatic fever in a untreated strep throat?

A

positive serologic tests (ASO)*

will be negative for the bacteria in the throat or blood

42
Q

why will rhumatic fever damage the heart, joints, skin andbrain?

A

Anti-streptococcal antibodies cross-react with tissues of the heart (mitral and aortic valves) *

43
Q

what is rheumatic heart disease?

A

damage to the mitral and aortic valces (stenosis) 10-20 years after infection

44
Q

what is acute glomerulonephritis?

what does it present with?

A

immune-complex disease

present with: hematuria, proteinuria, smoky/coal-colored urine

45
Q

what has to happen to get glomerulonephritis strep pyogenes related?

A

Follows cutaneous infection, or pharyngitis *

46
Q

how do you test for glomerulonephritis?

A

positive anti-DNAse B & ASO

47
Q

What antibody tests do you use to verify rheumatic fever?

A

positive ASO for ARF *

48
Q

What test do you use to differentiate strep pyogenes from staph aureus?

A

PYR test positive for strep pyogenes

49
Q

how does strep pyogenes look under the microscope?

A

gram positive chains

50
Q

how do you treat group A diseases?

A

penicillin

51
Q

how do you treat pharyngitis by group A streptococcus?

A

oral penicillin/amoxicillin

52
Q

what if patient is allergic to penicillin, and they are afflicted with strep throat?

A

erythromycin

53
Q

how do you treat impetigo caused by strep A?

what about impetigo caused by staph aureus?

A

nafcillin

still use nafcillin

54
Q

strep throat penicillin will prevent development of what disease?

A

rheumatic fever

55
Q

what is DNases (streptodornases)?

why are they important?

A
  • Depolymerize free DNA
  • Antibodies to DNase B imp. marker for diagnosis of antecedent skin/throat infections *

Microbiology Block 2 (30 decks)

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