The Microbiota in Health and Disease Flashcards
What is the likely cause of inflammation in IBD?
Dysregulated host immune response to the gut microbiota
Describe the role of microbe in the development in IBD
Increased mucosal bacterial load is present
Show reduced bacterial diversity (In IBD, but in IBS there is an altered diversity)
Broad spectrum antibiotics can have some efficacy in reducing symptoms
IBD does not occur in germ free animals
Reduced temporal stability in microbiota composition
Why is it hard to disentangle cause and effect when assessing IBD microbiota?
Many features of IBD itself could affect the microbiota
What features of IBD could affect the microbiota?
- Antibiotic use (•Reduced bacterial diversity and increases in Enterobacteriaceae can occur as a result of broad-spectrum antibiotic use)
- Inflammation (•causes reduced bacterial diversity and an increase in enterobacteriaceae)
- Diarrhoea
- Host diet
- Host genotype
What diseases are associated with changes in the gut microbiota?
IBS
IBD
Colorectal cancer (Fusobacterium, E.Coli)
Diabetes (includes opportunist pathogens)
CDAD - lack of diversity
Is there a difference in gut microbiota in inflamed vs non-inflamed tissue?
No
What is the microbiota in Chron’s disease like?
Enterobacteriaceae appeared to be slightly elevated in Crohn’s disease patients
What are probiotics?
Probiotics are live microorganisms which, when administered in adequate amounts confer a health benefit on the host
What are prebiotics?
A fermented food or ingredient that affects the activity / composition of the gut microbiota and cause a resultant health benefit to the host. (food for resident bacteria)
Give examples of Pre biotics
FOS, Inulin, GOS, Lactulose
Natural sources include garlic leeks and onion
Give examples of health benefits associated with prebiotics
Improves calcium uptake
Can increase stool frequency which reduces the risk of colon cancer (Native chicory inulin)
What is the mechanism of action for probiotics?
- Competition
- Bioconversions (diet)
- Production of vitamins
- Direct antagonism (pathogens)
- Competitive exclusion
- Barrier function
- Reduce inflammation
- Immune stimulation
What is the effect of probiotics on the prevention of GI diseases?
Beneficial in treatment and prevention of GI diseases
Which diseases do probiotics have a therapeutic effect on?
CDAD, antibiotic associated diarrhoea, helicobacter pylori, IBS
How do you combat a reduction in faecalibacterium prausnitzii?
Provide specific prebiotics designed to boost numbers of F. prausnitzii
Design F. prau as a biotherapeutic agent (medical probiotic)
How do you combat an increase in enterobacteriaceae?
Reduce antibiotic use to prevent decline in commensals
Include more dietary fibre in diet to boost bacterial diversity
What is the effect of a FODMAP diet? Used to treat IBS
(fermentable oligosaccharides, disaccharides, monosaccharides and polyols)
Diet designed to reduce bacterial fermentation; identifies key foods to exclude permanently
What is the effect of prebiotics?
Improved gut function
Management of inflammatory bowel disease, reduction in inflammatory markers
Prebiotics increase gut transit and therefore reduce the risk of colon cancer (reduced DNA damage and cell proliferation, faster gut transit)
Prebiotics (FOS/Inulin) increase calcium absorption and bone health
Consumption of prebiotics instead of sugars can lower glycaemic index (consumption of foods containing non-digestible carbohydrates instead of sugars induces a lower blood glucose rise after meals compared to those containing sugars)
What are the effects of antibiotics on the gut microbiota?
Most antibiotics are broad-spectrum antibiotics - active against target pathogen but also ‘kill’ commensal bacteria
There is a loss of diversity and there exists opportunity for pathogen colonisation – example – clostridium difficile - expands to occupy empty niches following antibiotic therapy.
What is the effect of overgrowth of C. Diff?
Results in toxin production, abdominal pain, fever (CDAD)
c diff associated diarrhoea
C diff spores are resistant to antibiotics
What is the effect of C diff strains that are antibiotic resistant?
Recurring C diff infections
What is FMT?
Faecal microbial transplantation
Sample from screened healthy volunteer donor transplanted into recipient (enema, colonoscopy, naso-enteric tube, capsules)
Donor microbiota repopulates large intestine, displaces c diff, prevents reinfection
Are there any clear cut contraindications for the application of fecal material transplantation?
NO
Take Home messages
Changes in gut microbiota composition may be associated with diseases - this does not always mean they CAUSE the disease
Antibiotics kill pathogenic bacteria causing disease AND kill many of the commensal, resident bacteria that may be important for health
Clostridium difficile can over-grow and cause disease following antibiotic therapy
The most effective treatment for recurring CDAD is properly provided FMT
Probiotics are added live bacteria that can be used to treat the symptoms of some disease
but different probiotics have different activities –
make sure the required activity has been scientifically proven with that specific probiotic
Prebiotics are a dietary food for the resident gut microbiota
– and can boost numbers of beneficial bacteria that use them for growth
