Microbiota of the GI tract Flashcards
why does bacterial colonisation change throughout the GI tract?
difference in conditions affects the colonisation:
PH
02 concentration
transit time
as you go down the GI tract, what is the main trend in bacterial colonisation?
increase in bacterial density
increase in obligate anaerobes
what is the importance of dietary fibre?
increases faecal bulk
eases faecal passage
reduces transit time
what is the main role of the microbiota in our gut?
digest dietary fibre which produces short chain fatty acids
what are the 3 main short chain fatty acids which bacteria produce?
butyrate
propionate
acetate
what is the SCFA and resulting function of the firmicutes bacteria?
butyrate
polyssacharide utilisation
what type of bacteria produces lactate?
actinomycetes
what is the main function of the lactic acid and sulphate reducing bacteria?
mucin degraders
how does our gut bacteria act as defence against pathogens?
active competition
mucous barrier
PH inhibition
in the colon, where is there more disease and why?
the distal colon (left) because the PH increases thereby creating more of a suitable environment for colonisation of bacteria
(optimal PH for bacteria growth is >6 and the PH in distal colon is 6.5)
if SCFA binds to FFAR2 receptor what effect will this have?
GLP-1 secretion
= inhibition of fat accumulation
is SCFA binds to FFAR3 receptor, what effect will this have?
PYY secretion
improves insulin resistance and satiety signalling in the brain
if SCFA binds to GPR109A, what effect will this have?
produce anti-inflammatory cytokine i.e. IL-10
suppress colonic inflammation and carcinogenesis
what are the factors which affect the gut microbiota?
diet environment lifestyle disease antibiotics probiotics prebiotics faecal transplant
what is the bacterial diversity like in someone with IBD?
Reduced bacterial diversity
a reduction in firmicutes and an increase in facultative anaerobes i.e. E.coli
patients with CD also have decreased numbers of F.prausnitzii
what are the features of IBD which could affect the microbiota and how?
antibiotic use - reduces diversity and increases enterobactericeae
inflammation - increases mucosal barrier which increases 02 consumption which altered microbial composition
diarrhoea - decreased transit time alters microbial composition
host diet - eat less fibre changes microbial composition
host genotype
how can you manipulate the microbiota in someone with IBD to relieve symptoms?
provide specific probiotics deigned to boost number of F.Prausnitzii (reduced in CD)
reduce antibiotic use
include more fibre to the diet
apply a low FODMAP diet (reduces bacterial fermentation)
use existing probiotics/prebiotics
what are probiotics?
live microorganisms - added to increase microbial diversity
what are probiotics?
a substrate that is selectively utilised by host microogranisms - it feeds the microbiota helping them grow
name some of the prebiotics.
GOS/Insulin
FOS
Lactulose
what are the health benefits associated with probiotics?
improved gut function
management of IBD
may reduce risk of colon cancer
FOS/insulin increase Ca absorption and bone health
GOS/FOS supplementation of infant formula increase bifidobacterial numbers
consumption of prebiotics instead of sugar can lower glycaemic index
how does prebiotics improve gut health?
stool bulking
faster transit time
what are the consequences of antibiotic use on gut health?
antibiotic exposure decreases microbiota diversity - increase in bacteriodetes and a decrease in actinobcacteria and proteobacteria
C.Diff grows rapidly to occupy empty niches which can lead to CDAD and maybe recurrent C.Diff infections
what is the treatment for recurrent C.Difficile infection?
antibiotics or faecal microbial transplant
why is FMT successful in treating recurrent Clostridium difficile infection but not IBD?
recurrent C.difficile infection is caused by the dysbiosis of gut microbiota
whereas the dysbiosis of the microbiota is caused by the inflammation, therefore by restoring gut microbiota it will only have a minor effect and not resolve the inflammation
what is the presentation of overgrowth of C.Dificile?
toxic production = abdominal pain, fever, c.diff associated diarrhoea
