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MIM 2 > 23. Streptococcal Respiratory Infections > Flashcards

23. Streptococcal Respiratory Infections Flashcards

1
Q

M types associated with ARF, AGN, STSS/NF

A

Rheumatic fever: M3, M5, M18, M19, M24
Glomerulonephritis: M49, M57, M59-61
Toxic Shock/Fascitis: M1, M3, M5

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2
Q

Cell and Culture Characteristics of streptococcus in general (3)

A
  • Spherical, grow in chains
  • may ferment diff carbs, but ALL produce lactic acid as end product (homolactic fermenters)
  • acidifying environment (lactic acid)–cause tooth decay
  • Alpha/Beta/Gamma hemolysis (green,clear)
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3
Q

Streptococcus Classifications (3 ways)

A
  1. Pyogenic (pus producing), Viridans (alpha hemolysis), enterococcus, lactic group.
  2. Hemolysis type (alpha/beta/gamma)
  3. Lancefield system is most reliable. Based on antigen of group C polysaccharide.
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4
Q

Streptococcus Characteristics (4)

A
  1. Gram positive, facultative anaerobes.
  2. Catalase negative
  3. Milk, water, dust, vegetation
  4. Most are saprophytic, some opportunistic or overt pathogens
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5
Q

Can only type ____ with lancefield system

A

Beta-hemolytic s. Pyogenes.

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6
Q

Lancefield system is based on ___, uses ___ against the antigen. What are the LF groups?

A
  • group-specific “C substance” (antigens) that are wall polysaccharides or teichoic acids.
  • Rabbit antiserum against the antigen.
  • 5 Lancefield groups: A to G.
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7
Q

Which species is the only member of Group A Strep?

A

S. pyogenes, which is beta-hemolytic.

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8
Q

How do you identify S. pyogenes?

colony, susceptibility, LF test, cells.

A
  • on sheep blood agar: domed, grayish, opalescent, BETA hemolysis (CLEAR)
  • ALL are susceptible to Bacitracin
  • Positive with Lancefield Group A antiserum (latex agglutination–get clumps).
  • Gram ++++ , Catalase negative (-), cocci in chains
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9
Q

What is the rapid strep test?

A

Lancefield A agglutination test used in primary care offices.

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10
Q

Strep pyogenes envelope composition

A
  • capsule - hyaluronic acid (low immunogenicity bc we have it in our ICM), protects against phagocytosis
  • thick peptidoglycan layer of cell wall (typical Gm+, has NAG, NAM, oligopeptide)
  • cell wall has protein antigens M, T, R, F
  • cytoplasmic memb.
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11
Q

What is the host defense against GAS?

A

Opsinophagocytosis. PMN, IgG, Complement.

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12
Q

M protein

A
  • TRUE virulence factor for GAS/s. pyogenes, cell wall protein antigen.
  • over 100 types, Ab against one M protein does not work against another.
  • Adhesin; antiphagocytic; degrades complement component C3b (Opsonin)
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13
Q

How does the Capsule function as a virulence factor?

A

Antiphagocytic, protects from phagocytosis.

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14
Q

Immune response to s. pyogenes involves ___ (remember: extracellular pathogen).

A
  • IgM, IgG
  • Neutrophils or PMN
  • complement (C3b-opsonin, C5a-chemotaxis)
    • antibody and complement opsonize these extracellular organisms, then neutrophils phagocytize (with FC receptors that bind C3b). **
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15
Q

s. pyogenes uses lipoteichoic acid to __ (think virulence)

A

Binds to epithelial cells

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16
Q

M-like protein

A

Binds IgM, IgG, and protease inhibitor a-macroglobulin

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17
Q

Only ____ can cause rheumatic fever

A

Streptococcus pyrogens strains with type I M protein.

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18
Q

Pyrogenic exotoxins (SpeA, SpeB) as s. pyogenes virulence factors

A
  • 7 of them.

- Superantigens – activate large numbers of CD4 T cells. MITOGENIC.

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19
Q

virulant factors of s. pyogenes that causes hemolysis

A

Streptolysins S and O—Cytotoxins; broad spectrum.

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20
Q

Virulent factor that allows SP to spread (spreading factor)

A

Streptokinase – lyses blood clots

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21
Q

How does SP combat Neutrophils? (which virulence factors)

A

DNase – cleaves free floating bacterial DNA in purulent material (exocytosed by neutrophils). A way to escape NETS (extracellular traps set by neutrophils–bacterial DNA studded with bact prot).

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22
Q

SP virulance factor: Opacity factor

A

Increases opacity of serum, binds fibronectin, lipoproteinase (adhesin)

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23
Q

SP combats complement attack using 2 virulence factors:

A

M protein – degraded complement component C3b (an opsonin) – escape opsonization.
C5a peptidase – degrades C5a (chemotactic factor)

24
Q

What glycolytic enzymes are found on surface of SP?

A

G3PD, Enolase – act as adhesins

25
Q

How SP combats antibodies:

A

M-like protein – binds IgM and IgG.

26
Q

Diseases that result from local infection with GAS (3)

A
  1. Pharyngitis.
  2. Scarlet fever
  3. Streptococcal pyoderma
27
Q

What causes Scarlet Fever?

A

Erythrogenic toxin encoded in bacteriophage

28
Q

What causes Streptococcal Pyoderma (Impetigo)?

A
  • s. pyogenes strains with M protein 49-60

- common in school kids, co-contamination with staph aureus.

29
Q

Diseases resulting from invasion of GAS (4)

A
  1. Erysipelas - skin
  2. Puerperal fever - uterus
  3. Sepsis - traumatic or surgical wounds
  4. Toxic schock syndrome and necrotizing infections
30
Q

Puerperal Fever

A
  • Uterine infection.

- caused by GAS, GBS.

31
Q

toxic shock and necrotizing infections are usually caused by ___ , key feature ___

A
  • s. pyogenes strains – M1, M3, M5 (M protein)

- Disproportionate pain to injury.

32
Q

Diseases from Post-Streptococcal Disease (2)

A
  1. Rheumatic fever
  2. Glomerulonephrits
    These are caused be molecular mimicry between M protein and the formation of immune complexes.
33
Q

What is rheumatic fever?

A

Gel and Coombs TII Autoimmune disease caused by molecular mimicry of the M protein to collagen. Binds heart, CNS, skeletal muscle.

34
Q

rheumatic fever

A

Cardiac problems, migratory rash, subcutaneous nodules, arthritis.

35
Q

How do we test for post streptococcal diseases (rheumatic fever and acute glomerular nephritis)?

A
  • Ab to streptolysin O (ASO titer) >250 indicates recent GAS infection.
  • Anti-DNase antibodies are diagnostic and better correlation with AGN
36
Q

What is acute glomerulonephritis?

A

T III Gel and Coombs. Immune complex disease. Affects kidney. Reversible.

36
Q

How is glomerulonephritis tested?

A

Increased Ab for DNase.

37
Q

Identification of S. pneumoniae

A
  1. Capnophilic (grows well in 5% CO2), domed, gray, mucoid, surrounded by ALPHA hemolysis (green)
  2. Gram-positive, catalase negative, DIPLOCOCCI
  3. susceptible to detergents Optochin and bile
  4. Quellung reaction - capsular swelling with homologous antiserum
38
Q

S. Pneumoniae envelope composition

A

Capsule, C polysacchride (TA), F antigen (LTA), Phosphocholine (TA and LTA), Pneumococcal surface protein.

39
Q

Pneumonia VF: Capsule

A

Prevents entrapment in the nasal mucus. Inhibits opsonophagocytosis.

40
Q

Pneumonia VFs in Upper Airway Colonization (7)

A
  1. Capsule
  2. ChoP
  3. NanA, BgaA, StrH
  4. Hyl
  5. PavA
  6. Eno
  7. CbpA
41
Q

Pneumonia VF in upper airway

A

Bacteriocin

42
Q

Reservoir for Pneumonia is ___, carrier rate ___

A
  • Nasopharynx

- Up to 60%

43
Q

Not all ____ capsules equally invasive

A

Pneumonia

44
Q

Which streptococcus does not usually cause a primary infection?

A

S. Pneumonia

45
Q

Which blood cell is involved in s. pneumonia infections?

A

PMN (neutrophils)

46
Q

Which diseases does pneumonia cause? (3)

A
  1. Otitis media (BIOFILM!)
  2. Respiratory pneumonia
  3. Meningitis
47
Q

Bacteriocin

A

Pneumonia VF -> Targets members of the same species.

48
Q

How do Ab against S. Pyogenes work?

A

Opsonic; promote phagocytosis

49
Q

What occurs after S. pyogenes infection?

A

ab against Streptolysin O increases

50
Q

How do Ab against S. Pyogenes work?

A

Opsonic; promote phagocytosis

51
Q

How many pneumococcal capsule types in the vaccine? Protects against __% of infections.

A

23 types – protects against 90% of infection.

52
Q

What is Puerperal Fever? What is it caused by?

A

Uterine infection in pregnant women, aka Childbed fever. Virus gets into blood stream from placenta during delivery.
Group A Strep, but now Group B.

53
Q

What do pneumonia Ab target?

A

Capsule

54
Q

Strep pyogenes envelope composition

A

Gram positive Ag: peptidoglycan, maramyl dipeptide, techoic acid, lipotechoic acid, M protein.

55
Q

What is the host defense against GAS?

A

Opsinophagocytosis. PMN, IgG, Complement.

MIM 2 (14 decks)

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