Intestinal Microbiome

Question 1

What does the intestinal microbiome contain?

Answer 1

• Bacteria
• Viruses
• Fungi
• Phages (bacterial viruses)
• Yeast
• Archaea (single-celled organisms)

Question 2

Types of bacteria in the microbiome

Answer 2

• Bystanders, just happy to be there because environment suits them
• Symbionts –> good bacteria that serve functional purposes
• Pathogenic –> cause disease

Question 3

How does a newborn acquire microbiome from their mother?

Answer 3

• Passing through the birth canal
• Breastfeeding

Question 4

Purposes/functions of the intestinal microbiome

Answer 4

• Host defence/pathogen invasion
• Nutrient/digestion/vitamins/metabolic processes
• Immune system development
• Intestinal epithelial maintenance cell renewal
• Gut-brain axis

Question 5

How does the intestinal microbiome fulfil its purpose involving nutrients/digestion/vitamins/metabolic processes?

Answer 5

• Fermentation of carbohydrates we are unable to digest (makes short chain fatty acids –> energy source)
• Improved lipid digestion
• Synthesis of vitamin K + aspects of vitamin D
• Activation of ‘pro-nutrients’
• Biotransformation of bile

Question 6

How does the intestinal microbiome contribute to immune system development?

Answer 6

• Host’s immune system is constantly surveying the microbial landscape
  > The bacteria are integral to development of this relationship
  > Recognition of pathogens, allergies, etc.
• During infancy the immune system learns to become tolerant to the bacteria, otherwise they would be destroyed

Question 7

What factors alter composition of the intestinal microbiome?

Answer 7

• Diet
• Medications
• Age

Question 8

What is microbial dysbiosis?

Answer 8

Imbalance of the microbial/host equilibrium, alteration in the bacterial communities present

Question 9

What is a healthy microbiome?

Answer 9

• Diverse + rich
• Ability to resist change easily (core set of ‘members’)
• Undertakes required metabolic processes

Question 10

Importance of short chain fatty acids

Answer 10

• Energy source (intestinal + systemic)
• Increase mucin secretion
• Improve epithelial barrier
• Dampen inflammatory cytokines
• BBB integrity + alteration of mood
• Anti-inflammatory effects
• Blood pressure/cardio-protection

Question 11

What are enterotypes?

Answer 11

Composition of bacterial populations in the intestinal microbiome

Question 12

What are enterotypes?

Answer 12

Composition of bacterial populations in the intestinal microbiome

Question 13

3 enterotypes

Answer 13

• Enterotype 1:
  > High abundance of Bacteroides bacteria
  > People who eat a lot of meat
• Enterotype 2:
  > High abundance of Prevotella
  > People who eat lots of carbohydrates
• Enterotype 3:
  > High abundance of Ruminococcus bacteria
  > Unknown what diet causes it

Question 14

3 types of microbiome manipulating therapies

Answer 14

• Prebiotics
• Probiotics
• Faecal microbial transplantation (FMT)

Question 15

What are prebiotics?

Answer 15

Nutrients (carbs + oligosaccharides) that are delivered to the colon in a formulation to support the growth of bacteria

Question 16

What are probiotics?

Answer 16

Formulations that contain microorganisms, which when taken in appropriate doses + protected in certain ways, can reach the colon intact and viable. They are able to engraft, colonise + promote intestinal health

Question 17

What is faecal microbial transplantation?

Answer 17

Transfer of a processed stool obtained from a healthy donor into a patient, aiming to correct the underlying dysbiosis by attempting to restore the intestinal microbial community

Question 18

By what routes can faecal microbial transplantation be administered?

Answer 18

• Colonoscope
• Naso-gastric tube

Question 19

Problems with faecal microbial transplantation

Answer 19

• Pathogenic transmission
• Strict inclusion criteria (2.8% of people eligible)
• Routes of delivery (invasive, costly, require hospitalisation, associated complications)
• Dedication (repeated administration is impractical if it becomes routine)
• Heterogenous nature (difficult to point out where exactly bioactive agent is and ensure in each ‘dose’)