27-01-23 - Gut Microbiota and Immunity Flashcards
Learning outcomes
- Identify the factors which affect the microbiota of the gastrointestinal tract
- Explain the basic interactions of the microbiota with the body’s immune system
- Extrapolate the effect of disturbances of the normal microbiota
- Explain the basis of the host-bacteria relationships in the gastrointestinal tract
- Identify the various causes of gastrointestinal infection and intoxication
What is the human microbiome?
What is microbiota?
- Human microbiome - the combined genetic matter of the micro-organisms residing on the human body
- Microbiota - the micro-organisms which reside in a particular community e.g. gut microbiota, skin microbiota
What are 4 parts of the innate immune system?
What is part of the adaptive immune system?
- 4 parts of the innate immune system
1) Physical Barriers .eg skin
2) Physiological processes e.g acid, saliva
3) Inflammation
4) Natural killer (NK) cells
- T and B lymphocytes are part of the adaptive immune system
- B lymphocytes produce immunoglobulins
What are the number of genes in the human genome?
What are the number of genes in the microbiome of the GI tract?
How many more bacteria in the GI tract than cells in the body?
- Human Genome - 23 000 genes
- Microbiome - 3 000 000 genes
- There are 10 times more bacteria in our GI tract than cells in our body
What 2 ways does the mouth defend against disease?
- 2 ways does the mouth defend against disease:
1) Flow
* The flow of Saliva moves things through the oral cavity into the pharynx and the oesophagus
* Stasis is a bad thing – stoppage of normal flow of fluids, as bacteria can build-up and cause infection
2) Saliva
* Antimicrobials – IgA
* Microbiota - microbes that naturally reside in the mouth
What 3 ways does the oesophagus defend against disease?
What is Boerhaave syndrome?
- 3 ways does the oesophagus defend against disease:
1) Flow of liquids
2) Peristalsis
3) Mucous membranes - Boerhaave syndrome, is a spontaneous perforation of the esophagus that results from a sudden increase in intraesophageal pressure combined with negative intrathoracic pressure (eg, severe straining or vomiting)
What adaptations help the stomach defend against disease?
What is the pH of the stomach contents?
What cells in the stomach produce acid?
- The stomach acid can defend against disease using enzymes and stomach acid
- The pH of the stomach contents is 1-3
- Parietal cells in the stomach produce acid
Which bacteria is able to survive in the stomach?
When might we test for H. Pylori?
How do we treat H. Pylori?
- Helicobacter pylori is a bacterium can survive in the stomach
- We may test for H. Pylori when a patient has reflux and dyspepsia (indigestion), which can cause heart burn, bloating and nausea
- We treat H pylori infections using triply therapy – 2 antibiotics and a proton pump inhibitor (PPI) to reduce stomach acid
What are defensins?
What defensive are found in the stomach?
- Defensins are antimicrobials
- They are peptides that can kill bacteria and viruses through a variety of mechanisms.
- In the stomach they are beta defensins.
What 6 ways does the small intestine defend against disease?
- 6 ways does the small intestine defend against disease:
1) Flow of gut contents
2) Peristalsis
3) Mucus
4) Secretory IgA - important as can pass through mucosal membranes
5) Antimicrobial peptides - A defensins
6) Microbiota
What is SIBO?
What symptoms can it have?
What 2 types of drugs have been implicated?
What condition is SIBO associated with?
- SIBO is a clinical condition due to overgrowth of bacteria in the intestine
- Presents with a variety of symptoms: diarrhoea, to malabsorption
- 2 types of drugs that have been implicated:
1) PPIs
* Proton pump inhibitors
* Reduce stomach acid levels
2) Opioids
* E.g morphine or codeine
* Slows down the GI tract, potentially causing stagnation
- SIBO is associated with IBS
What 4 ways does the large intestine defend against disease?
- 4 ways the large intestine defends against disease:
1) Peristalsis
2) Mucus
3) Shedding and replication of epithelium
4) Microbiota
Where can the bacterium E. Histolytica be found?
What are symptoms of infected individuals?
In what % of cases does it cause disease?
What is part of its mechanism?
- The bacterium E. Histolytica adheres to epithelial layer of gut wall
- Often infected individuals are asymptomatic, thought to cause disease in 10% of cases
- Part of E. Histolytica’s mechanism for doing this is secreting an enzyme which cleaves mucin, the main component of the mucus layer
Describe the effects of commensal, symbiotic, and parasitic bacteria on hosts (in picture)
What are 3 common and friendly gut bacteria?
What are their 2 mechanisms of action?
- 3 common and friendly gut bacteria:
1) Lactobacillus
2) Bifidobacterium
3) Bacteroides - Their 2 mechanisms of action:
- Bacteria such as these - which are also found in common probiotics - are acid producing, promoting an acidic environment which is less favourable to harmful bugs
- They also produce bacteriocins- antimicrobial peptides which can harm other bacteria, but not the bacteria itself
Health and disease in the GIT diagram (in picture)
What are probiotics?
What are they usually added to?
What conditions can they improve?
Probiotics to prevent colds (in picture)
- Probiotics are live bacteria and yeasts promoted as having various health benefits.
- They’re usually added to yoghurts or taken as food supplements
- The evidence does exist for certain conditions e.g. proctitis in Inflammatory Bowel Disease
- Evidence seems to be increasing that can have positive effects on health with little negative side effects or risks
- Probiotics to prevent colds (in picture)
