immunology of the Gut

Question 1

what are the 4 major phyla of bacteria

Answer 1

remember PAFB

Proteobacteria
Actinobacteria
Firmicutes
Bacteroidetes

Question 2

microbiota function

Answer 2

Essential nutrients; ​

metabolism of indigestible compounds; ​

defence against colonisation of pathogens

Question 3

what factors cause dysbiosis

Answer 3

infection/inflammation
diet
xenobiotic
hygiene
genetics

Question 4

dysbiosis meaning

Answer 4

change in bacterial distribution within the gut– associated with adverse health outcomes–>

pathobiont expansion and decreased diversity

Question 5

4 physical barrier for mucosal defence

Answer 5

Anatomical
-Epithelial barrier
-Peristalsis

Chemical
-Enzymes
-Acidic pH

Question 6

where are MALT found and what is it surrounded by

Answer 6

submucosa below epithelium. surrounded by HEV(high endothelial venules) postcapillary venules- easy passage of lymphocytes

lots in oral cavity

Question 7

examples of non-organised GALT

Answer 7

Intra-epithelial lymphocytes
Lamina propria lymphocytes

Question 8

4 examples of organised GALT

Answer 8

-Peyer’s patches (small intestine)
-Isolated lymphoid follicles
-Caecal patches (large intestine)
-Mesenteric lymph nodes (encapsulated)

Question 9

GALT - peyer’s patch -explain how it works

Answer 9

1. antigen uptake via M(microfold cells) within FAE
2. M-cells express IgA receptors- transfer IgA bacteria complex into Peyer’s patch
3. naive B-cells express IgM. Class switch to IgA. Matures-> IgA secreting plasma cells
4. populate lamina propria
5. secretory IgA binds to luminal antigen- prevent adhesion and invasion

Question 10

why does enterocyte have rapid turnover?
What happened if this is impaired (giving example of cause) ?

Answer 10

defence against pathogens &
protect cell function

ensure lesions- short-lived.

impaired production of new cells (e.g. radiation)= severe intestinal dysfunction

Question 11

cholera mechanism

Answer 11

Release cholera enterotoxin ​

=> binds small intestine epithelium ​

=> causes all the pumps and channels to actively release ions into lumen ​

=> water moves out as well

Question 12

what is cholera caused by

Answer 12

Vibrio Cholera Serogroup O1 + O139​

Question 13

cholera transmission

Answer 13

faecal-oral route
Spreads via contaminated water & food

Question 14

cholera diagnosis

Answer 14

gold standard: bacterial culture from stool sample on selective agar

rapid dipstick tests

Question 15

cholera treatment

Answer 15

oral-rehydration

vaccine- Dukoral-oral inactivated

Question 16

causes of infectious diarrhoea

Answer 16

viral
-rotavirus
-norovirus

bacterial
-campylobacter
-e.coli
-c.diff

Question 17

rotavirus- where does it replicate and what type is most common?
most common in what age?
treatment?
vaccination type and name?

Answer 17

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

Question 18

norovirus what?
transmission?
symptoms?
diagnosis?
treat?

Answer 18

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

Question 19

campylobacter (curved bacteria)
transmission and treatment

Answer 19

Transmission:
Undercooked meat, untreated water & unpasteurised milk
Low infective dose, can cause illness

Treatment:
Not usually required
Azithromycin (macrolide) is standard antibiotic

Question 20

c.diff management

Answer 20

Isolate patient (very contagious)

Stop current antibiotics

give Vancomycin

Faecal Microbiota Transplantation (FMT) – 98% cure rate

Question 21

e.coli 6 types

Answer 21

enterotoxigenic E.coli
enterohaemorrhagic/shiga toxin-producing E.coli
enteroinvasive E.coli

enteropathogenic E.coli
enteroaggregative E.coli
diffusely inherent E.coli

Question 22

what is enterotoxigenic E.coli

Answer 22

cholera like toxin

watery diarrhoea

Question 23

what is enterohaemorrhagic/shiga toxin producing e.coli

Answer 23

shigatoxin
7% get haemolytic uraemic syndrome- loss of kidney function

Question 24

enteroinvasive E.coli

Answer 24

shigella like illness
bloody diarrhoea

Question 25

difference between small and larger intestines in non-organised GALT

Answer 25

small- have paneth cells and microvilli

large-have inner and outer mucus layer. crypts not as deep as small intestines