Streptococci Flashcards
1
Q
What is Streptococci
A
- Streptococcus is genus of gram-positive coccus
2
Q
How does Streptococci divide?
A
- Spherical cells divide only in ONE PLAIN and form chains or pairs
3
Q
Does streptococci require complex media for growth?
A
- Yes
4
Q
What shaped cells are they?
A
- Spherical Cells (chained)
5
Q
What haem group are they unable to make ?
A
- Unable to make haem group of cytochromes or catalase
6
Q
What are Streptococci grown on ?
A
- Grown on blood agar (good source of catalase)
7
Q
What are the different groupings of Streptococci?
A
- Streptococci I: Hemolysis
- Streptococci II: Antigenically / Serologically
8
Q
What is the first grouping of Streptococcis?
A
-hemolysis
9
Q
How does Hemolysis work?
A
- Put on blood agar
- Looking into the pattern of haemolysis
10
Q
What are the different outcomes of haemolysis
A
- Beta, Alpha and Gamma hemolysis
11
Q
What is Beta haemolysis ?
A
- Complete lysis of the red blood cell
- Clear zone
12
Q
What is Alpha haemolysis?
A
- incomplete haemolysis of red blood cells
- Produce a greenish-brown zone
13
Q
What is Gamma haemolysis?
A
- no haemolysis at all
14
Q
What is the Lancefield Grouping for?
A
- For Beta - hemolytic Streps
- A, B, C, D …. W
- Based on the specific carbohydrate antigen extracted by heating cells up to 150 degrees
- About 20 groups
15
Q
What are the Group A Streptococcus ?
A
- Group A Strep = Streptococcus pyogenes
- Beta hemolytic
- Sensitive to bacitracin
- Causes many of the streptococcal diseases of humans
16
Q
Explain the importance of the Antigenicity of M-proteins of Group A Streptococcus
A
- Antigenicity of M-proteins in the cell wall provides sub-classification of group A into over 100 sub-serotypes