A14 - Human gut microbiota and their role in gut homeostasis I

The GI tract is the largest immune organ we have and contains more immune cells than any other organ

True or False?

True.

What is Mucosa?

The combination of

• The single layer of columnar epithelium

• Lamina propria (connective tissue)

• Muscularis mucosae (Thin smooth muscle layer)

What is the Submucosa?

Connective tissues below the Mucosa

What is Muscularis externa?

Muscle layer external to the Mucosa.

Contains two layers of muscle

• Circular muscle

• Longitudinal muscle

What is the Serosa?

Layer which contains

• Mesothelium

• Connective tissue

Secretes lubricating fluids and forms part of the peritoneum

What is the role of villi and microvilli?

To increase the surface area of the small intestine to allow for a larger area for diffusion

What do Paneth cells secrete?

Antimicrobial peptides

What are found between epithelial cells and allow the epithelial cells to act as a physical barrier?

Tight junctions are between the cells which help close the tiny gaps and ensure the epithelium is a physical barrier

How are stool samples ideally stored?

Fresh samples are ideally immediately frozen at -80°C and stored

What are the limits of stool samples for microbiota analysis?

• May not be representative of mucosa-associated microbes

• May not be reflective of proximal luminal contents

What are the three distinct phases of microbiota maturation during early life?

• Development (3-14 months old)

• Transition (15-30 months old)

• Stability (31-46 months old)

Breastfeeding has been associated with higher levels of which bacteria and lower levels of what other bacteria?

Higher levels of

• Bifidobacterium

• Lactobacillus rhamnosus

• Staphylococcus epidermidis

Lower levels of

• E. coli

What type of factors can influence the microbiota stability?

• Diet

• Antibiotics

• Travel

• Genetics

Why is microbiota stability important?

Commensal bacteria help supress proliferation and colonisation of pathogens

Insatiability can result in dysbiosis and a loss of commensal colonisation, allowing pathogens to proliferate and colonise

C. diff is a pathogenic bacteria which causes diarrhoea upon infection.

True or False?

False.

C. diff is part of the normal gut flora in 5% of the population

Usually doesn’t cause issues, however dysbiosis can result in a C. diff overgrowth which can cause symptoms

Why was the Faecal Microbiota Transplant (FMT) clinical trial stopped early?

Stopped early on ethical grounds

• FMT was so much more effective than standard care, it was unethical to not give everyone it

• Therefore the clinical trial was stopped

How are Faecal Microbiota Transplants (FMT) typically done?

Sample taken from a healthy donor (usually a family member)

• Sample is screened for blood born viruses

The transplant is usually done via an endoscopy with many water flushes

How can IBD affect the CNS?

The endothelial barrier in the brain choroid plexus tightens in response to intestinal inflammation through LPS

In mice, this causes a deficit in short-term memory and anxiety like behaviour