Gut microbiota in health and disease Flashcards
list some factors that might affect the gut microbiota
environment probiotics antibiotics prebiotics faecal transplant disease diet lifestage
what must you alway question if there is dysbiosis
whether it is the cause or consequence of a disease
give examples of diseases that can occur from microbes that normally live asymptomatically in the host
MRSA - staph aureus strep throat gingivitis acne meningitis pneumonia diarrhoea - c. diff thrush UTI gastric cancer - helicobactor pylori
give example of disease that occurs when a bacterium colonises in a different site from where it is meant to be
sepsis
where does the inflammation in IBD most likely come from
dysregulated host immune response to gut microbiota
give some examples of evidence of the role of microbes in IBD development
- Increased mucosal bacterial load is observed in IBD patients
- Broad spectrum antibiotics can have some efficacy in reducing symptoms
- Faecal stream diversion induces remission in Crohn’s disease
- IBD does not occur in germ-free animals
whats is the bacterial diversity like in patients with IBD
reduced diversity
often a reduction in firmicutes (gram+ve)
increase in facultative anaerobes (e.g. e.coli)
how does IBD manifest
non-uniformly - patients have regions of healthy tissue adjacent to inflamed regions
what features of IBD itself could affect the microbiota
antibiotic use inflammation diarrhoea host diet host genotype
what is the impact of antibiotics on gut microbiota
reduced bacterial diversity and increases in enterobacteriaceae can occur as a result of broad spectrum antibiotic use
what is the impact of inflammation on the gut
Reduced bacterial diversity and increases in enterobacteriaceae will occur as a result of inflammation
how does inflammation reduce bacterial diversity
vicious cycle:
inflammation
- decrease in mucus barrier
- increase in O2 exposure
- alters microbial composition
- increases inflammation
how can diarrhoea affect microbial composition
decreases transit time
how can the host diet affect microbial composition
desire to eat less fibre
define probiotics
live microorganisms which, when administered in adequate amounts
confer a health benefit on the host
i.e. ADDED LIVE BACTERIA to eg yogurt, supplements, etc
**beneficial in the treatment and prevention of GI diseases
define prebiotics
a substrate that is selectively utilized by host microorganisms
conferring a health benefit
i.e. FOOD for resident bacteria, found naturally in some plant foods, also can be added to biscuits, bread, drinks, yogurts, supplements, etc
what are the three main mechanism of action groups for probiotics
- widespread - genus or species relatively unimportant
- rare - ie strain specific effects
- frequent - genus or species important, strain relatively unimportant
what actions are present in widespread mechanisms
competition
competitive exclusion
barrier function
reduced inflammation
what actions are present in rare mechanisms
production of vitamins
what actions are present in frequent mechanisms
bioconversions (diet)
direct antagonism (pathogens)
immune stimulation
what are selected prebitoics that can affect microbiota
Fructo-oligosaccharides (FOS) and inulin
Galacto-oligosaccharides (GOS)
Lactulose
give some health benefits of prebiotics
Improved gut function - stool bulking and faster gut transit
Management of Inflammatory bowel disease - reduction in inflammatory markers
Reduce the risk of colon cancer - reduced DNA damage and cell proliferation, faster gut transit
Prebiotic (GOS/FOS) supplementation of infant formula - increases bifidobacteria numbers
Prebiotics (FOS/Inulin) increase calcium absorption and bone health - pH effect
Consumption of prebiotics instead of sugars can lower glycaemic index - induce a lower blood glucose rise after meals compared to those containing sugars
what are the different types of exposure to antibiotics
direct - e.g. taken orally, IV
indirect - e.g. cattle given antibiotics - still present when meat eaten
what do broad spectrum antibiotics cause
remove of target pathogen BUT also commensal bacteria
can also cause spread go antibiotic resistance
what are the consequences of antibiotic treatment
During and immediately post-antibiotic treatment - Decreased microbial diversity - Opportunity for pathogen colonisation - Results in pathogen dominated community
how can antibiotic use result in recurrent c.diff infections
Clostridium difficile expands to occupy
empty niches following antibiotic therapy
Overgrowth of C. difficile results in toxin
production, abdominal pain, fever (CDAD)
Clostridium difficile spores are resistant
to antibiotics
Some C. difficile strains are antibiotic resistant
Results in recurring C. difficile infections
what is the initial treatment for c diff associated diarrhoea (CDAD)
antibiotic therapy - cures 75%
what is the best treatment for recurrent CDAD when antibiotics DONT work
FMT (faecal microbial transplantation)
effective in >90% patients with recurring c diff infections
how does FMT work
Faecal sample from screened healthy volunteer donor transplanted into recipient
(enema, colonoscopy, naso-enteric tube, capsules)
Donor microbiota repopulates large intestine, displaces C. difficile, prevents reinfection
currently only approved for RECURRING CDAD
for what diseases is FMT NOT effective in producing disease remission
pouchitis (inflammation of the ileal pouch)
ulcerative colitis
what is an essential process for the donor in FMT to undergo
proper screening for all known pathogens
list some of the diseases gut microbes (or the products they create) are linked to
IBS IBD CV disease allergies obesity bone health brain health rheumatoid arthritis diabetes colorectal cancer
what diseases can prebiotics help with
colorectal cancer
diabetes
osteoporosis
