Microbiota of the GI tract

Question 1

why does bacterial colonisation change throughout the GI tract?

Answer 1

difference in conditions affects the colonisation:
PH
02 concentration
transit time

Question 2

as you go down the GI tract, what is the main trend in bacterial colonisation?

Answer 2

increase in bacterial density

increase in obligate anaerobes

Question 3

what is the importance of dietary fibre?

Answer 3

increases faecal bulk
eases faecal passage
reduces transit time

Question 4

what is the main role of the microbiota in our gut?

Answer 4

digest dietary fibre which produces short chain fatty acids

Question 5

what are the 3 main short chain fatty acids which bacteria produce?

Answer 5

butyrate
propionate
acetate

Question 6

what is the SCFA and resulting function of the firmicutes bacteria?

Answer 6

butyrate

polyssacharide utilisation

Question 7

what type of bacteria produces lactate?

Answer 7

actinomycetes

Question 8

what is the main function of the lactic acid and sulphate reducing bacteria?

Answer 8

mucin degraders

Question 9

how does our gut bacteria act as defence against pathogens?

Answer 9

active competition
mucous barrier
PH inhibition

Question 10

in the colon, where is there more disease and why?

Answer 10

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)

Question 11

if SCFA binds to FFAR2 receptor what effect will this have?

Answer 11

GLP-1 secretion

= inhibition of fat accumulation

Question 12

is SCFA binds to FFAR3 receptor, what effect will this have?

Answer 12

PYY secretion

improves insulin resistance and satiety signalling in the brain

Question 13

if SCFA binds to GPR109A, what effect will this have?

Answer 13

produce anti-inflammatory cytokine i.e. IL-10

suppress colonic inflammation and carcinogenesis

Question 14

what are the factors which affect the gut microbiota?

Answer 14

diet
environment
lifestyle 
disease 
antibiotics
probiotics
prebiotics
faecal transplant

Question 15

what is the bacterial diversity like in someone with IBD?

Answer 15

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

Question 16

what are the features of IBD which could affect the microbiota and how?

Answer 16

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

Question 17

how can you manipulate the microbiota in someone with IBD to relieve symptoms?

Answer 17

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

Question 18

what are probiotics?

Answer 18

live microorganisms - added to increase microbial diversity

Question 19

what are probiotics?

Answer 19

a substrate that is selectively utilised by host microogranisms - it feeds the microbiota helping them grow

Question 20

name some of the prebiotics.

Answer 20

GOS/Insulin
FOS
Lactulose

Question 21

what are the health benefits associated with probiotics?

Answer 21

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

Question 22

how does prebiotics improve gut health?

Answer 22

stool bulking

faster transit time

Question 23

what are the consequences of antibiotic use on gut health?

Answer 23

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

Question 24

what is the treatment for recurrent C.Difficile infection?

Answer 24

antibiotics or faecal microbial transplant

Question 25

why is FMT successful in treating recurrent Clostridium difficile infection but not IBD?

Answer 25

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

Question 26

what is the presentation of overgrowth of C.Dificile?

Answer 26

toxic production = abdominal pain, fever, c.diff associated diarrhoea