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IHD Part 2 306 > Gastro-intestinal system > Flashcards

Flashcards in Gastro-intestinal system Deck (71)
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1

Pathogens of the GI tract: What is gastroenteritis?

Syndrome characterised by GI-symptoms including nausea, vomiting, diarrhoea and abdominal pain

2

Pathogens of the GI tract: What is dysentery?

Abnormal inflammation of GI-tract: often blood and pus in faeces and pain, fever, abdominal cramps- often disease of large intestine

3

Pathogens of the GI tract: What is enterocolitis?

Inflammation of mucosa of small and large intestine

4

Pathogens of the GI tract: What are the defences present in the mouth?

Flow of liquids, saliva (statherins, defensins), lysozyme, normal bacterial flora

5

Pathogens of the GI tract: What are the defences in the oesophagus?

Flow of liquids, peristalsis

6

Pathogens of the GI tract: What are the defences in the stomach?

Acidic pH

7

Pathogens of the GI tract:What are the defences in the small intestine?

flow of gut contents
peristalsis
mucus
bile
secretary IgA
ymphoid tissue (Peter's patches)
shedding and replacement of epithelium
normal flora

8

Pathogens of the GI tract: What are the defences in the large intestine?

Normal flora
peristalsis
shedding and replication of epithelium
mucus

9

Pathogens of the GI tract: What two bacterium are common in causing food poisoning?

Staphylococcus aureus

Clostridium botulinum

Bacillus cereus - gram positive rod

10

Pathogens of the GI tract: how does helicobacter pylori resist stomach acid?

Produces Urease - produces ammonia cloud (neutralises acid) around organism that allows organism to survive and replicate

Protective cloud during transit to gastric mucin layer

can therefore inhabit gastric mucosa

bleeding/ulcers

Ammonia = basis of breath test

11

Pathogens of the GI tract: How is helicobacter pylori treated?

proton-pump inhibitor PLUS metronidazole/ amoxicillin and Clarithromycin

12

Pathogens of the GI tract: What is a major cause of diarrhoea?

E coli - gram neg rod

13

Pathogens of the GI tract: How is E coli detected in the lab?

macConkey agar

lactose fermentation - used for colour change when E coli grows

PCR and antigen tests used for serotypes

14

Pathogens of the GI tract: How does EPEC form attachments?

Bundle- forming pilli
needle injects toxins into host cell
sits on pedestal

has translocated intimin receptor (intimin mediates attachment to epithelial cells)

leads to watery diarrhoea

15

Pathogens of the GI tract: How does ETEC form attachments and what toxins does it produces?

via adhesive pilli
forms pedestals

Produce Heat Stable (ST) and Labile (LT) enterotoxins (cholera like) that cause diarrhoea

Produce Vero-toxin (Also called Shigella-like toxin)- STx
STx (verotoxin) is a potent diarrhoeal toxin (and has receptor on kidney cells ) acts via damaging cells directly, can damage blood vessels in kidneys

16

Pathogens of the GI tract: What organism can cause bacillary dysentry?

Shigella

low infectious dose - 10-100 cells needed

non lactose fermenters
common in poorer countries

spread faecal- orally

17

Pathogens of the GI tract: how is salmonella spread?

Spread from food- mainly chicken and dairy products, but also person to person

18

Pathogens of the GI tract: What cells does salmonella spread via?

Invade macrophages then to epithelium

doesn't cause lactose fermentation

19

Pathogens of the GI tract: What is salmonella associated with?

S. Typhi - typhoid fever

20

Pathogens of the GI tract: Where does S. typhi reside?

Gall bladder

21

Pathogens of the GI tract: how is s.typhi transferred?

oral- faecal route during food prep

22

Pathogens of the GI tract: What is the most common cause of food poisoning?

Campylobacter - gram neg micro-aeophiles

Campylobacter jejuni most common
Acquired by ingestion of contaminated food

23

Pathogens of the GI tract: what type of bacterium is cholera?

motile Gram-negative comma-shaped bacterium

24

Pathogens of the GI tract:What does colonisation of cholera of the SI depend on?

Motility (polar flagella)
production of mucinase
attachment to specific receptors

25

Pathogens of the GI tract: What effect does the cholera toxin have?

disruption of ADP-ribosylation of G-protein signalling pathways causes increased secretion of Chloride ions

This prevents influx of Sodium ions into cells

Results in rapid loss of water from tissue- massive diarrhoea

26

Pathogens of the GI tract: What is the treatment for cholera?

Rapid fluid and electolyte replacement required or dehydration and death result

27

Pathogens of the GI tract: What are the symptoms of cholera?

absent tears
very dry mouth and tongue
lethargic/ unconscious
sunken and dry eyes
drinks poorly or not able to drink
skin pinch goes back slowly

28

Pathogens of the GI tract: how can cholera be prevented?

Vaccines
best - improvement of water system and sanitation

29

Pathogens of the GI tract: What % of gastroenteritis cases are viral?

20

30

Pathogens of the GI tract: What is a rotavirus?

Wheel-like viral particle
Diarrhoea caused by tissue damage in small intestine
Dehydration main risk
Very low-infectious dose
Very contagious
V resistant to celaining products