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Pathology: Infectious disease section > Streptococci > Flashcards

Streptococci Flashcards

1
Q

what are some general characteristics of strep infections?

A

spreading of suppurative infections

-cellulitis, impetigo, erisypelas, GABHS

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2
Q

what are some post-strep hypersensitivity disease?

A
  • rheumatic fever

- immune complex glomerulonephritis

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3
Q

Group A strep is associated with?

A

GABHS, beta hemolytic,

  • S. pyogenes
  • pharyngitis/post strep disease
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4
Q

Group B strep is associated with?

A

peri-natal sepsis/newborn, UTI

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5
Q

Viridans strep is associated with?

A

not one species

  • alpha hemolytic,
  • major cause of subacute bacterial endocarditis
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6
Q

beta hemolytic strep

A
  • clear, complete hemolysis

- Pyogenes: Group A, bactracin sensitive

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7
Q

alpha hemolytic strep

A

green, partial hemolytic

  • Pneumoniae
  • Viridans
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8
Q

Pneumoniae strep

A

optochin sensitive

  • bile soluble
  • capsule-> quellung
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9
Q

Viridans strep

A

mutans, sanguis

  • optochin resistant
  • NOT bile soluble
  • no capsule
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10
Q

streptococcus mutans

A

major cause of dental caries

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11
Q

gamma-hemolytic strep

A

Enterococcus
-E. faecalis
E. faecium

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12
Q

what are the virulence factors of strep?

A
  • cell wall polysaccharides
  • capsules (M proteins)-> prevent phagocytosis
  • enzymes: streptokinase, streptolysin O,S
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13
Q

enzymes streptokinase, streptolysin O,S help strep to do what?

A

contribute ability to spread through tissues (cellulitis)

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14
Q

what does strep erythrogenic toxin do?

A

skin rash

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15
Q

what is the hosts response to strep?

A

antibodies to both capsular antigens and exotoxins

  • M protein of many subtypes is antiphagocytic
  • antibodies help in preventing recurrent pharyngeal infections in some
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16
Q

antibodies to which strep can cross react to cause rheumatic fever?

A

Group A

  • S. pyogenes
  • deposition of immune complexes in kidney-> poststreptococcal glomerulonephritis
17
Q

What infections are associated with Group A strep?

A

GABHS or GAS

  • acute pharyngitis/UPT-> redness, edema, pain, fever, chills
  • punctate abscesses in tonsillar crypts
  • peritonsillar, retropharyngeal abscess formation

Scarlet fever

  • ages 3-15, erythrogenic toxin, violaceous red rash on trunk
  • strawberry tongue
  • associated with poststreptococcal sequelae
18
Q

what are some post-streptococcal sequelae?

A

post-streptococcal glomerulonephritis:

rheumatic fever

19
Q

post-streptococcal glomerulonephritis

A

1-2 week after strep

  • self-limited
  • immune-complex mediated
  • can see signs of acute renal failure->oliguria, hematuria, hypertension
20
Q

rheumatic fever

A

weeks-months and beyond

  • worse with repeated infections
  • acute: fever, joint disease, myocardial and valvular disease
  • corresponds to streptolysin O titers in blood
  • NO bacteria present (autoimmune cross reactivity)
  • if chronic: long standing damage to mitral and aortic heart valves
21
Q

strep infections: cellulitis, pyoderma

A

redness, swelling and pain

  • less localized than staph infections
  • abscesses are rare, and so are necrotizing fasciitis
22
Q

strep infections: impetigo

A

contagious skin infection in kids involving horny layers of skin

  • could be due to staph
  • can be due to GABHS (S. pyogenes) with post-strep sequelae
23
Q

strep infections: erysipelas

A
  • groups A/C
  • warm climates
  • erythematous skin involvement without suppuration
24
Q

necrotizing fasciitis, “flesh eating disease”

A

uncommon, deep-seated soft tissue infection-> soft tissue gangrene

  • Fournier’s gangrene-> scrotal/perineal form
  • pre-existing immunodeficiency, diabetes
  • subcut. strep infection with necrosis that is overtaken by anaerobes-> Gas formation on X-ray
  • 50-70% mortality
25
Q

subacute bacterial endocarditis

A

S. viridans, transient bacteremia following dental work

  • left sided valvular endocarditis
  • previously damaged heart valves at greater risk
  • prophylactic antibiotics for dental work
26
Q

puerperal sepsis

A

perinatal

-group B strep

27
Q

what are pathological features with suppurative inflammation with cellulitis

A

diffuse interstitial neutrophilic infiltrates with minimal destruction of host tissue

  • less likely to cause discreet abscesses like staph infections
  • often deeper lesions which spread further than staph infections
  • redness, pain, erythrogenic/pyrogenic toxins causes fever, rash
28
Q

what are some ways to diagnose GABHS

A

rapid strep test-> has group A strep carbohydrate antigen
-confirmation culture 12-48 hours-> catalase negative, antibiotic specificity

rheumatic fever test: anti-streptolysin O Ab titers

29
Q

impetigo is most common with

A

strep

30
Q

why is necrotizing fasciitis common is those with diabetes?

A

lack of neutrophil function in diabetes because they are hyperglycemic, which is toxic to neutrophils

31
Q

what do anti-streptolsyin O ab titers measure?

A

measure level of bodies response, not antibodies

Pathology: Infectious disease section (11 decks)

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