immunology of the Gut Flashcards
what are the 4 major phyla of bacteria
remember PAFB
Proteobacteria
Actinobacteria
Firmicutes
Bacteroidetes
microbiota function
Essential nutrients;
metabolism of indigestible compounds;
defence against colonisation of pathogens
what factors cause dysbiosis
infection/inflammation
diet
xenobiotic
hygiene
genetics
dysbiosis meaning
change in bacterial distribution within the gut– associated with adverse health outcomes–>
pathobiont expansion and decreased diversity
4 physical barrier for mucosal defence
Anatomical
-Epithelial barrier
-Peristalsis
Chemical
-Enzymes
-Acidic pH
where are MALT found and what is it surrounded by
submucosa below epithelium. surrounded by HEV(high endothelial venules) postcapillary venules- easy passage of lymphocytes
lots in oral cavity
examples of non-organised GALT
Intra-epithelial lymphocytes
Lamina propria lymphocytes
4 examples of organised GALT
-Peyer’s patches (small intestine)
-Isolated lymphoid follicles
-Caecal patches (large intestine)
-Mesenteric lymph nodes (encapsulated)
GALT - peyer’s patch -explain how it works
- antigen uptake via M(microfold cells) within FAE
- M-cells express IgA receptors- transfer IgA bacteria complex into Peyer’s patch
- naive B-cells express IgM. Class switch to IgA. Matures-> IgA secreting plasma cells
- populate lamina propria
- secretory IgA binds to luminal antigen- prevent adhesion and invasion
why does enterocyte have rapid turnover?
What happened if this is impaired (giving example of cause) ?
defence against pathogens &
protect cell function
ensure lesions- short-lived.
impaired production of new cells (e.g. radiation)= severe intestinal dysfunction
cholera mechanism
Release cholera enterotoxin
=> binds small intestine epithelium
=> causes all the pumps and channels to actively release ions into lumen
=> water moves out as well
what is cholera caused by
Vibrio Cholera Serogroup O1 + O139
cholera transmission
faecal-oral route
Spreads via contaminated water & food
cholera diagnosis
gold standard: bacterial culture from stool sample on selective agar
rapid dipstick tests
cholera treatment
oral-rehydration
vaccine- Dukoral-oral inactivated
causes of infectious diarrhoea
viral
-rotavirus
-norovirus
bacterial
-campylobacter
-e.coli
-c.diff
rotavirus- where does it replicate and what type is most common?
most common in what age?
treatment?
vaccination type and name?
RNA virus replicated in enterocyte (type A most common in human)
most common cause of diarrhoea in young kids
treatment- oral rehydration therapy
vaccination-live attenuated oral vaccine (rotarix)-against Type A
norovirus what?
transmission?
symptoms?
diagnosis?
treat?
RNA virus with incubation period 24-48hrs
Transmission:
Faecal-oral transmission.
Individuals may shed infectious virus for up to 2 weeks
often -closed communities
Symptoms:
Acute gastroenteritis, recovery 1 – 3 days
Diagnosis:
Sample PCR
no treatment needed
campylobacter (curved bacteria)
transmission and treatment
Transmission:
Undercooked meat, untreated water & unpasteurised milk
Low infective dose, can cause illness
Treatment:
Not usually required
Azithromycin (macrolide) is standard antibiotic
c.diff management
Isolate patient (very contagious)
Stop current antibiotics
give Vancomycin
Faecal Microbiota Transplantation (FMT) – 98% cure rate
e.coli 6 types
enterotoxigenic E.coli
enterohaemorrhagic/shiga toxin-producing E.coli
enteroinvasive E.coli
enteropathogenic E.coli
enteroaggregative E.coli
diffusely inherent E.coli
what is enterotoxigenic E.coli
cholera like toxin
watery diarrhoea
what is enterohaemorrhagic/shiga toxin producing e.coli
shigatoxin
7% get haemolytic uraemic syndrome- loss of kidney function
enteroinvasive E.coli
shigella like illness
bloody diarrhoea
difference between small and larger intestines in non-organised GALT
small- have paneth cells and microvilli
large-have inner and outer mucus layer. crypts not as deep as small intestines
