Basics

Question 1

What must a pathogen do to cause disease?

Answer 1

Enter body. 
Colonise host.
Evade defences.
Multiply, disseminate.
Damage.

Question 2

How does skin act as a barrier against colonisation?

Answer 2

Physical barrier.

shedding, acidic, dry, salty, lower temp, competition

Question 3

How do mucosal surfaces act as a barrier against colonisation?

Answer 3

Physical barrier.

Shedding, mucous with lactoferrin, lysozyme, antimicrobial peptides (defensins), pH, peristalsis, cilia, competition

Question 4

What structures can he adhesins?

Answer 4

Pilli, afimbiral adhesins, capsules

Question 5

Why might a pathogen invade?

Answer 5

Obligate intracellular parasite.
Hide from immune response.
Disseminate to deeper tissue.

Question 6

How might a pathogen invade?

Answer 6

Invasins are mediators. Host cell responds to bacterial trigger, cell cytoskeleton altered

Question 7

What host defenses need to be evaded? How are they evaded?

Answer 7

Soluble factors (complement, antibodies). 
Avoid complement fixation, destroy antibodies, avoid antibody detection (host mimicry, e.g. capsule B and salic acid) 

Phagocytes (macrophages, neutrophils)
Avoid phaogocytosis (avoid opsonisation), kill phagocyte (toxins, apoptosis), survive inside phagocyte