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Medical bacteriology: First half > GI tract infections > Flashcards

Flashcards in GI tract infections Deck (18)
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1
Q

How many bacteria in the colon per gram of faeces?

A

1 billion

2
Q

What does the faecel flora have the metabolic capacity of?

A

The liver

3
Q

Bacteria in the GI tract

A

Obligate anaerobes such as bacterioides outnumber facultative bacteria by 100:1

4
Q

Bacterial roles in the GI tract

A

Synthesising vit k and B12

Digesting tryptophan as a neuroprotectant

5
Q

How many cases of diarrhoeal disease per year?

A

1.7 billion

6
Q

Bacterial causes of diarrhoeal disease

A
  • Salmonella
  • Shigella
  • Bacillus cereus
  • E.coli
  • Campylobacter
  • Staph
  • Clos difficile
  • Vibrio cholerae
7
Q

Bacteria that adhere

A
  • E.coli
  • Shigella sonnei
  • Campylobacter
  • Salmonella
8
Q

Cholera

A
  • Vibrio cholerae
  • Rice water stool
  • Spread by faecel oral route
  • Kills 95,000 people a year
  • We have an oral vaccine and oral rehydration
9
Q

Cholera toxin

A
  • cholera toxin has 2 subunits (a and b)
  • alpha subunit ribosylates G proteins so cAMP is ribosylated
  • b subunit binds to the gangliosides and is translocated into the cell
10
Q

What do S. enterica, S. enteritidis and S. typhimurium contaminate?

A

Poultry; egg layers vaccinated in 1993

11
Q

Entry of salmonella into the cells?

A

Via bacterial mediated endocytosis and the whole bacteria moves via the tight junction which disrupts it .
They can target macrophages

12
Q

Which bacteria has a type III secretion system? What does this do?

A

Salmonella enterica
Injects effector molecules from the bacterial cytosol to the eukaryotic cytosol.
activates GTPases Rho and Rac which leads to the binding up of the membrane so lysozomes can’t fuse

13
Q

E.coli O157

A

Enterohaemorragic and has a shiga like toxin via pathogen island

14
Q

C. difficile infections

A

Toxin mediated
Toxin A and B are 300kDa in size
Can colonise after antibiotic use and disrupt the membrane leading to pseudomembrane collitis, diarrhoea and toxic megacolon
Toxin A and B are very similar to human proteins so can be internalised by the receptor. Acidification activates the toxin and it moves outside the vacuole. Rho and Rac modification causes cell death and tight junction disruption.

15
Q

What does campylobacter cause?

A
  • Food poisoning
  • Reactive arthritis
  • Guillan-Barres syndrome
  • IBS
16
Q

Where is campylobacter obtained from?

A

Uncooked meat, unpasteurised milk and untreated water

17
Q

Campylobacter mechanism of action

A

Proteins on the surface of campylobacter are similar to those on neurons so neurons can be targeted.
Can arrest cell cycle division at the G2 phase.

18
Q

Treating gastroenteritis

A

Antibiotics are only used in the very young, very old or in a campylobacter infection