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MIM 2 > 23. Streptococcal Respiratory Infections > Flashcards

23. Streptococcal Respiratory Infections Flashcards

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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:

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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?

Study These Flashcards
A

G3PD, Enolase – act as adhesins

25
How SP combats antibodies:
M-like protein -- binds IgM and IgG.
26
Diseases that result from local infection with GAS (3)
1. Pharyngitis. 2. Scarlet fever 3. Streptococcal pyoderma
27
What causes Scarlet Fever?
Erythrogenic toxin encoded in bacteriophage
28
What causes Streptococcal Pyoderma (Impetigo)?
- s. pyogenes strains with M protein 49-60 | - common in school kids, co-contamination with staph aureus.
29
Diseases resulting from invasion of GAS (4)
1. Erysipelas - skin 2. Puerperal fever - uterus 3. Sepsis - traumatic or surgical wounds 4. Toxic schock syndrome and necrotizing infections
30
Puerperal Fever
- Uterine infection. | - caused by GAS, GBS.
31
toxic shock and necrotizing infections are usually caused by ___ , key feature ___
- s. pyogenes strains -- M1, M3, M5 (M protein) | - Disproportionate pain to injury.
32
Diseases from Post-Streptococcal Disease (2)
1. Rheumatic fever 2. Glomerulonephrits These are caused be molecular mimicry between M protein and the formation of immune complexes.
33
What is rheumatic fever?
Gel and Coombs TII Autoimmune disease caused by molecular mimicry of the M protein to collagen. Binds heart, CNS, skeletal muscle.
34
rheumatic fever
Cardiac problems, migratory rash, subcutaneous nodules, arthritis.
35
How do we test for post streptococcal diseases (rheumatic fever and acute glomerular nephritis)?
- Ab to streptolysin O (ASO titer) >250 indicates recent GAS infection. - Anti-DNase antibodies are diagnostic and better correlation with AGN
36
What is acute glomerulonephritis?
T III Gel and Coombs. Immune complex disease. Affects kidney. Reversible.
36
How is glomerulonephritis tested?
Increased Ab for DNase.
37
Identification of S. pneumoniae
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
S. Pneumoniae envelope composition
Capsule, C polysacchride (TA), F antigen (LTA), Phosphocholine (TA and LTA), Pneumococcal surface protein.
39
Pneumonia VF: Capsule
Prevents entrapment in the nasal mucus. Inhibits opsonophagocytosis.
40
Pneumonia VFs in Upper Airway Colonization (7)
1. Capsule 2. ChoP 3. NanA, BgaA, StrH 4. Hyl 5. PavA 6. Eno 7. CbpA
41
Pneumonia VF in upper airway
Bacteriocin
42
Reservoir for Pneumonia is ___, carrier rate ___
- Nasopharynx | - Up to 60%
43
Not all ____ capsules equally invasive
Pneumonia
44
Which streptococcus does not usually cause a primary infection?
S. Pneumonia
45
Which blood cell is involved in s. pneumonia infections?
PMN (neutrophils)
46
Which diseases does pneumonia cause? (3)
1. Otitis media (BIOFILM!) 2. Respiratory pneumonia 3. Meningitis
47
Bacteriocin
Pneumonia VF -> Targets members of the same species.
48
How do Ab against S. Pyogenes work?
Opsonic; promote phagocytosis
49
What occurs after S. pyogenes infection?
ab against Streptolysin O increases
50
How do Ab against S. Pyogenes work?
Opsonic; promote phagocytosis
51
How many pneumococcal capsule types in the vaccine? Protects against __% of infections.
23 types -- protects against 90% of infection.
52
What is Puerperal Fever? What is it caused by?
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
What do pneumonia Ab target?
Capsule
54
Strep pyogenes envelope composition
Gram positive Ag: peptidoglycan, maramyl dipeptide, techoic acid, lipotechoic acid, M protein.
55
What is the host defense against GAS?
Opsinophagocytosis. PMN, IgG, Complement.

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