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Flashcards in Streptococcus Deck (24):
1

Streptococcus general characteristics (6):

1. Gram positive.
2. Cocci arranged in pairs or chains.
3. Non-motile.
4. Facultative anaerobic or capnophilic.
5. Catalase negative.
6. Complex nutritional requirements: blood or serum enriched media for isolation.

2

Streptococcus pyogenes (7):

Group A Streptococcus
1. Gram positive.
2. Facultative anaerobe.
3. Capsule (hyaluronic acid).
4. Beta-hemolytic.
5. M-proteins (80 types).
6. F-protein bind fibronectin.
7. Bacitracin sensitive.

3

Major virulence factors for group A Streptococcus (8):

1. Capsule.
2. M proteins.
3. C5a peptidase.
4. DNase.
5. Streptolysin O and S.
6. Hyaluronidase.
7. Streptokinase.
8. Pyrogenic/erythrogenic exotoxins.

4

Biological actions of strep pyogenes capsule:

Non-immunogenic and anti-phagocytic.

5

Biological actions of C5a peptidase:

Anti-chemotactic and reduces inflammation mediated by C5a.

6

Biological actions of streptokinase:

Promotes bacterial spread into tissues by breaking down blood clots.

7

Streptolysin O (2):

Oxygen labile
- Lyses leukocytes, platelets and erythrocytes.
- Immunogenic, indicating a recent GAS infection (ASO test).

8

Streptolysin S (4):

Oxygen-stable
- Lyses leukocytes, platelets and erythrocytes.
- Stimulates release of lysosomal enzymes.
- Beta-hemolysis.
- Non-immunogenic.

9

DNase (4):

- Four distinct forms (A, B, C, D).
- Anti-DNase B: Important marker of cutaneous GAS infection especially in those who failed ASO test.
- Depolymerizes cell free DNA in pus (reduction of viscosity).
- Contributes to spread from local site.

10

Suppurative streptococcal diseases (5):

1. Pharyngitis.
2. Scarlet fever.
3. Impetigo.
4. Cellulitis (#1).
5. Erysipelas.

11

Scarlet fever (3):

- Occurs when the infecting strain is lysogenized by a bacteriophage that produces a pyrogenic exotoxin.
- Red maculopapular rash on trunk --> extremities.
- White and red "strawberry" tongue.

12

Impetigo (2):

Purulent with crusting
- Colonization is due to direct contact with an infected person or fomites.
- Regional lymph nodes enlarged but lack systemic signs.

13

Erysipelas (2):

- Localized pain, inflammation, lymph node enlargement and systemic signs.
- Historically on the face but becoming more common on the legs.

14

Non-Suppurative streptococcal disease (2):

No GAS present.
- Acute glomerular nephritis.
- Acute rheumatic fever.

15

Acute glomerular nephritis (4):

AGN
- Acute inflammation of renal glomeruli with edema, HTN, hematuria and proteinuria.
- Post-pharyngitis or post-skin infection (after resolution).
- Facial edema, smoky urine.
- Type III hypersensitivity.

16

Acute rheumatic fever (5):

ARF
- Pancarditis.
- No GAS present.
- Post pharyngitis only.
- Due to cross-reactivity of anti-M protein antibody with human cardiac tissue.
- JONES symptoms.

17

Streptococcus agalactiae (7):

Group B Streptococcus
1. Gram positive.
2. Cocci in pair.
3. Capsule.
4. CAMP test positive.
5. Beta-hemolytic.
6. Threat to infants infected perinatally.
7. Responsible for post-partum endometritis.

18

Streptococcus agalactiae virulence factors (2):

- Capsule.
- Sialic acid - capsular component, inhibits alternate pathway of complement.

19

Streptococcus pneumoniae (8):

1. Gram positive.
2. Cocci in pairs or short chains.
3. Capsule.
4. CAMP test negative.
5. Bile soluble (bile causes lysis).
6. Aerobically alpha-hemolytic; anaerobically beta-hemolytic.
7. Catalase negative.
8. Optochin sensitive.

20

Streptococcus pneumoniae virulence factors (5):

1. Capsules.
2. Robust biofilm formation.
3. IgA proteases cleaves IgA.
4. Ahesins - mediate attachment to epithelial cells.
5. Pneumolysin - destroys the ciliated epithelial cell.

21

Streptococcus pneumonia infections (4):

MOPS
1. Meningitis (#1 adult).
2. Otitis media (#1).
3. lobar Pneumonia (#1 adult).
4. Sinusitis (#1).

22

Enterococcus (8):

1. Gram positive.
2. Catalase negative.
3. Bacitracin resistant.
4. Variable hemolysis.
5. Can grow in up to 6.5% NaCl.
6. Bile resistant.
7. Can hydrolyze esculin.
8. Cocci in pairs or short chain.

23

Enterococcus virulence factors (5):

1. Aggregation substance.
2. Carbohydrate adhesins.
3. Cytolysin - inhibits gram positive bacteria and induces local tissue damage.
4. Gelatinase.
5. Antibiotic resistant.

24

Streptococcus viridans (7):

- Gram positive.
- Alpha hemolytic.
- Optochin resistant.
- No Lancefield antigens.
- Sub-acute endocarditis (#1).
- Dental carries.
- Normal flora of mouth and teeth.