M5: Streptococci & Disease Flashcards
1
Q
List some general characteristics of Streptococcus genus (4)
A
- Gram positive (stains purple from thick peptidoglycan wall)
- Facultative anaerobe
- Catalase negative
- Chain-forming cocci
(occur in spheres)
2
Q
What is the only exception to the chain-forming in spheres characteristic in the Streptococcus genus?
A
S. pneumoniae
3
Q
The following 3 bacteria are non oral streptococci, what diseases do they cause?
- S. pyogenes
- S. agalactiae
- S. pneumoniae
A
- Wide spectrum diseases and severities
- Neonatal infections and Bovine mastitis
- Pneumonia
4
Q
What are the 3 main types of haemolysis observed on blood agar?
A
- b-heamolysis (complete RBC clearance)
- α-haemolysis (partial RBC clearance)
- No clearance
5
Q
Streptococci are fermenters what does this mean?
A
Break down carbohydrates into acids
6
Q
Streptococcus pyogenes;
Skin infections? (2) Upper respiratory tract? (2) Toxin mediated? Systemic? Post streptococcal infection? (2)
A
- Impetigo
- Erysipelas
- Tonsillitis
- Pharyngitis
- Scarlet fever
- Septicaemia
- Rheumatic fever
- Acute glomerulonephritis
7
Q
What are the virulence factors for Streptococcus pyogenes? (3)
A
- Surface components
- C5a peptidase (inhibits phagocytosis)
- Extracellular products
