Streptococcus

Question 1

Streptococcus general characteristics (6):

Answer 1

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.

Question 2

Streptococcus pyogenes (7):

Answer 2

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.

Question 3

Major virulence factors for group A Streptococcus (8):

Answer 3

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

Question 4

Biological actions of strep pyogenes capsule:

Answer 4

Non-immunogenic and anti-phagocytic.

Question 5

Biological actions of C5a peptidase:

Answer 5

Anti-chemotactic and reduces inflammation mediated by C5a.

Question 6

Biological actions of streptokinase:

Answer 6

Promotes bacterial spread into tissues by breaking down blood clots.

Question 7

Streptolysin O (2):

Answer 7

Oxygen labile

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

Question 8

Streptolysin S (4):

Answer 8

Oxygen-stable

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

Question 9

DNase (4):

Answer 9

• 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.

Question 10

Suppurative streptococcal diseases (5):

Answer 10

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

Question 11

Scarlet fever (3):

Answer 11

• 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.

Question 12

Impetigo (2):

Answer 12

Purulent with crusting

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

Question 13

Erysipelas (2):

Answer 13

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

Question 14

Non-Suppurative streptococcal disease (2):

Answer 14

No GAS present.

• Acute glomerular nephritis.
• Acute rheumatic fever.

Question 15

Acute glomerular nephritis (4):

Answer 15

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.

Question 16

Acute rheumatic fever (5):

Answer 16

ARF

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

Question 17

Streptococcus agalactiae (7):

Answer 17

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.

Question 18

Streptococcus agalactiae virulence factors (2):

Answer 18

• Capsule.

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

Question 19

Streptococcus pneumoniae (8):

Answer 19

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.

Question 20

Streptococcus pneumoniae virulence factors (5):

Answer 20

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.

Question 21

Streptococcus pneumonia infections (4):

Answer 21

MOPS

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

Question 22

Enterococcus (8):

Answer 22

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.

Question 23

Enterococcus virulence factors (5):

Answer 23

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

Question 24

Streptococcus viridans (7):

Answer 24

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