Commensals and Pathogens

Question 1

What is the nature of human microbiota (3)

Answer 1

1. The human microbiota consists of bacteria that live in symbiosis with the host without causing harm.
2. They are part of the normal flora or microbiota
3. They have a role in digestion, synthesis of vitamins K, B2, B7, B9 & B12, immune system and regulation.

Question 2

Differentiate between commensal and pathogenic bacteria and their clinical significance (7)

Answer 2

With probiotics, we have:
1. enhanced barrier function, mucus secretion
2. colonisation
3. bacteriocin, SCFA release leading to
4. prevention of pathogens, viral infections

With pathogenic bacteria, we have:
1. damaged barrier function
2. inflammatory cytokine cancer factor secretion
3. bacterial and viral infections

Question 3

What is the clinical significance of pathogenic bacteria (6)

Answer 3

1. More gut inflammation
2. More risk of CVD (Cardiovascular disease)
3. More LPS production
4. Less short-chain fatty acids
5. More risk of infections
6. More insulin resistance

Question 4

What is the clinical significance of commensal bacteria (6)

Answer 4

1. Less gut inflammation
2. Improved lipid metabolism
3. More antioxidants production
4. More short-chain fatty acids
5. Less risk of infections
6. More insulin sensitivity

Question 5

What is the concept of opportunistic pathogens

Answer 5

Opportunistic pathogens are pathogens which infect people with weakened immune systems (immunocompromised/taking immunosuppressants).

Question 6

Show knowledge of the modes of pathogen transmission and types of virulence factors (8)

Answer 6

1. Adherence components (attachment)
2. Capsules (evasion)
3. Invasion enzymes (entry into host, colonisation)
   
   1. hyaluronidase
   2. collagenase
   3. fibrinolytic enzymes (e.g. streptokinase)
   4. coagulase
   5. various other proteases, nucleases, lipases