19. Streptococcus

Question 1

What type of gram bacteria are streptococci?

Answer 1

• Gram positive cocci

- in chains

Question 2

How are streptococci classified by haemolysis?

Answer 2

• alpha haemolysis
• beta haemolysis
• gamma haemolysis

Question 3

What is alpha haemolysis and how does it appear on agar?

Answer 3

• partial haemolysis

- produced dark green colour on blood agar

Question 4

Define viridans and which type of haemolysis do these streptococci show?

Answer 4

Viridans means green

- viridans streptococci are alpha haemolytic

Question 5

What is beta haemolysis and how does it appear on agar?

Answer 5

• complete haemolysis

- produces translucent/yellow area on blood agar

Question 6

What is gamma haemolysis?

Answer 6

• no haemolysis

- non-haemolytic streptococci

Question 7

What is Lancefield classification?

Answer 7

Serological classification of beta-haemolytic streptococci, based on cell wall antigens

Question 8

What is the major group A strep?

Answer 8

Strep pyogenes (pyogenic )

Question 9

What are the classifications of S. pneumoniae?

Answer 9

• NA
• α
• viridans (but can be pyogenic)

Question 10

What is S. pneumoniae associated with?

Answer 10

• Pneumonia

Can produce a polysaccharide capsule and get into the blood stream:
- meningitis, endocarditis, peritonitis