2.4: Streptococcus Pyogenes

Question 1

What morphology do streptococci have when they grow

Answer 1

They grow on a single axis and form long chains or pairs

Question 2

Do Strep. Pyogenes have a capsule, what is it made up of?

Answer 2

Yes, it is encapsulated. The capsule is made out of Hyaluronic acid

Shown: Hot Apple (pie) in an capsule on the counter

Question 3

Is Strep. Pyogenes’ capsule immunogenic?

Answer 3

No. Hyaluronic acid is made by our CT all over our body.

Hence, the capsule of Strep. Pyogenes is not immunogenic bc it is made out of Hyaluronic acid

Question 4

How do we classify Strep. Pyogenes by hemolysis?

Answer 4

Beta-hemolytic.

Beta-hemolysis (β-hemolysis), sometimes called complete hemolysis, is a complete lysis of red cells in the media around and under the colonies: the area appears lightened (yellow) and transparent.[1] Streptolysin, an exotoxin, is the enzyme produced by the bacteria which causes the complete lysis of red blood cells.

Question 5

Pyogenic infections (3)

Answer 5

Impetigo: Pyogenic skin infections said to look “honey-crusted” (shown by honey-crusted lemon pie)
Remember: Impetigo can also be caused by Staph. Aureus.

Pharyngitis / Strep throat: (shown by red scarf)

Cellulitis: Inflammation of deeper skin layers, orange skin.
Erysipelas: Acute infection, after trauma, very superficial cellulitis infection with well demarkated borders.
(Both shown with red gloves as errythema of skin)

Question 6

Toxin mediated diseases (3)

- Toxigenic syndromes caused by which toxins

Answer 6

Strep. Pyagonease Toxin (strep pyrogenic exotocin, SPE)
SpeA - Superantigen (TSLS)
SpeB - Protease (Nec. Fasc.) - (B for burnt gingerbread)
SpeC - Superantigen (TSLS)

Scarlet fever: 3 main symptoms

1. Redning/swelling of tongue (aka. strawberry tongue)
2. Pharyngitis (shown by red scarf)
3. Wide, diffuse rash that spares the face (everywhere except the face) - (Shown by gingerbread)

Toxic shock like syndrome - TSLS (very similar to Staph. Aureus’s shock)
- Toxic shock-like syndrome mediated by a superantigen (shown with cape, with lightning = shock)
The toxin work as a superantigen

Necrotizing fasciitis (Refered to as Flesh eating bacteria)

• caused by toxigenic strains by Strep. Pyogenes
• invade fascia underlying the skin and spread very rapidly (surgical emergency!) - (shown by the black Gingerbread, with amputated leg - due to necrotizing)

Question 7

Post-streptococcal diseases:

Rheumatic fever

Answer 7

Rheumatic fever (type 3 hypersensitivity): Preventable with antibiotic treatment
M protein: highly antigenic protein in the Strep. Pyogenes’ cell wall, and the main virulence factor responsible for Rheumatic fever.
2 ways it acts as a virulence factor:
- inferferse with obstinusation (?), thus anti-phagocytic (shown as master chef push away man trying to eat)
- Elicit a very strong humoral response -> great chance to create antibodies to a very similar self-antigen, which is the myocin in our cardiac muscle (the process called molecular mimicry)
This means: M-protein mimics the myosin in our heart, causing our own antibodies to attack our heart. This causes very big problems especially for Mitral valves -> Mitral valves are damaged in RF -> cause Mitral Stenosis (Mitral valved are named after the Miter hat that the pope wears, so does the master chef on pic)

Rheumatic fever starts after Strep. pharyngitis infection
- So: Pharyngitis can precipitate RF
- does NOT happen after skin infection or if pharyngitis is correctly treated (why RF is more common in young children, little access to healthcare)
(Shown with red scarf on master chef)

Symptoms of RF: 5 major Criteria (JONES)
J: Joints - Polyarthritis (why the name RF in first place)
O (shape of heart): Heart problems