Streptococcus pneumonia Flashcards
What is the most common microbe that causes pneumonia?
Streptococcus pneumonie
What does pneumonia cause in the lungs, and what is the result?
Alveoli to become inflamed Fluid and pus containing bacteria fills air space This results in limited respiratory exchange, and can lead to other infection as it spreads elsewhere through blood vessels
What are meninges, and how do they relate to pneumonia?
Meninges are the protective layer of the brain and spinal cord. Dissemination of pneumonia especially occurs in meninges, leading to pneumococcal meningitis
What type of gram is S. pneumonie?
Gram positive
What does diplococcus mean?
The bacteria tend to stay in pairs S. pneumoniae is diplococcus
What is otitis media?
A middle ear infection, which can be caused (especially in children) by S. pneumoniae
What are the two main virulence determinants for S. pneumoniae?
Polysaccharide capsule
Pneumolysin
What is the main function of the polysaccharide capsule?
Capsule interferes with opsonophagocytosis Makes S. pneumoniae extremely effective at evading phagocytosis
What are the two different variants of S. pneumoniae?
T and O variant
What are the main features of the T variant?
Transparent
Low level of capsule
Adheres well to host cells
What are the main features of the O variant?
Opaque Abundant level of capsule Resists phagocytosis
When is S. pneumoniae each variant?
T variant when binding to cells, O variant when already bound
What is pneumolysin?
Active toxin of S. pneumoniae, which penetrates and destroys membranes
How does pneumolysin work?
Binds to cholesterol in host cell membranes, forming large pores.
What is the impact of pneumolysin on the host?
Disrupts integrity of cell, leading to cell lysis/death. Can also facilitate spread of bacteria into other, deeper tissue (e.g. meninges)
