S. pneumoniae Flashcards
1
Q
natural flora in which parts of the body?
A
nasal cavity, upper respiratory tract
higher levels in young children and the elderly
2
Q
pathenogenesis
A
- neuraminidase
- pneumolysin: from pore to promote inflammation
- lytA: forms pore
3
Q
immune system evasion
A
- pspA & pspC: bind choline for survival
- psaA, piaA & piuA: bind metals (iron) for survival
- polysaccharide capsule
- Factor H: inhibits complement cascade
- DNAases: break down NETs from neutrophils
4
Q
gram stain
A
- gram positive diplococcus
5
Q
media, colonies & antibiotics
A
- HBA produces green colonies (alpha haemolytic)
- sensitive to optochin
6
Q
why is the capsule so important?
A
- prevents phagocytosis and opsonisation
- hides PAMPs
- hydration and protection in a harsh dry environment
- negative charge repels mucus
- basis of classification and vaccine production
7
Q
bacterial transformation experiment
A
- live, un-capsulated pneumococcus: mouse survived
- dead, encapsulated pneumococcus: mouse survived
- live un-capsulated & dead encapsulated: mouse died (dead encapsulated was cultured from mouse)
8
Q
laboratory diagnosis
A
- colonise sample from lung on HBA
- bile solubility: bile salts break cell wall of pneumococci but not other streptococci
- PCR of capsule genes
9
Q
vaccine
A
conjugate polysaccharide vaccine with B & T cell determinants
