Bacteria host interaction

Question 1

How and what do bacteria adhere to

Answer 1

To:
Cells
Secretory products
Structural components
Other bacteria

Structures involved:
Fimbrae/pili (Most common adhesive structure in gram negative bacteria - e.g. E. coli)
Adhesive macromolecules imbedded in membrane (e.g. streptococcus)
Capsules
Flagellum

Question 2

How do pathogens cause signs of infection

Answer 2

Toxins – directly damage host tissues – cause tissue necrosis, fever & shock

Invasion – invade host tissues – cause tissue damage & inflammation

Replication – replicate within host cells – cell death & tissue damage

Question 3

How does host cell response to bacterial invasion cause signs of infection

Answer 3

Inflammatory response – cytokines released cause fever, pain & tissue damage

Immune cell activation – neutrophils & macrophages activated – causes tissue damage & inflammation

Complement activation – cause inflammation & tissue damage

Question 4

What are virulence factors & genes

Answer 4

Virulence factors = molecules that allow bacteria to adhere, invade, evade host defence, cause tissue damage, replicate or persist in host

Virulence gene = gene encoding for virulence factor

Horizontal transfer of virulence genes (plasmids) –> rapid evolution

Question 5

How do bacteria exploit host cells

Answer 5

Use host cell actin filaments to move within host cell & spread to adjacent cells
e.g. listeria & Shigella

Manipulate host cell’s cytoskeleton to form specialised structures
e.g. salmonella

Manipulate host cell metabolic pathway to obtain essential nutrients
e.g. chlamydia

Manipulate host immune cell signalling pathways to evade detection by immune system
e.g. tuberculosis