Lecture 4 - Gram Positive Cocci (STREP) Flashcards
1
Q
Streptococci
A
- Arranged in pairs or chains
- Grows on blood agar
2
Q
Streptococci:
Groups
A
- haemolytic properties (alpha, beta)
- carboydrate C antigen (Lancefield classification)
- M-protein
- —> divides beta-haemolytic
- —>mostly group A
3
Q
Haemolytic Phaemolytic Properties:
Alpha
A
- Greenish brown
- Partially destroys RBC
4
Q
Haemolytic Phaemolytic Properties:
Beta
A
- Destroys completely the RBC
- Clear zone around colonies
5
Q
Carbohydrate C Antigen
A
- Extracted from the cell wall, subdivides streptococci in groups A-T (lancer field)
6
Q
M-Protien
A
- Permits subdivision of beta-haemolytic streptococci into over 70 serotypes
- Mostly in group A
7
Q
Haemolytic Phaemolytic Properties:
Gamma
A
Not hemolytic
8
Q
Group A, beta-hemolytic, Streptococcus pyogenes causes:
A
- acute tonsillitis (strept throat) – can lead to rheumatic heart disease
- impetigo, cellulitis, etc. (skin infections)
- fever and septicaemia
9
Q
Streptococcus pyogenes:
Caused by toxins
A
- streptolysins (O and S)
• neutrophils and macrophages - streptococcal pyrogenic exotoxins (Spes)
• scarlet fever rash
10
Q
Streptococcus pyogenes:
Enzymes
A
- Hyaluronidase (helps spreading of bacteria)
- Virtually all are penicillin G sensitive
- Transmission by direct contact (nasal is more easily transmitted)
- Contaminated food can cause outbreaks
11
Q
Streptococcus pyogenes:
Prevention
A
- Education of health personnel
- Aseptic obstetric procedures (puerperal fever)
- Early detection and treatment
12
Q
Necrotizing Fasciitis
A
- Streptococcus pyogenes culprit
- Does not actually “eat” anything
- Toxin is responsible for damage
13
Q
Necrotizing Fasciitis:
How does it happen? Theories
A
- hijacking human plasminogen from blood, attach to surface and
activate it into protease…good for spreading… - bacteriophage has gene encoding for enzyme allowing bacteria to escape entrapment and killing by neutrophils (white blood cells)
14
Q
Group B: Streptococcus agalactiae
A
- Found in vagina of health women (can cause neonatal infections)
15
Q
Group B: Streptococcus agalactiae
Early Septicaemia
A
- respiratory distress or shock at birth
- high fatality rate (serious)
