L6 - Gastrointestinal Tract Infections Flashcards
Which region of the body harbours the most commensal bacteria?
Colon - 10^11
Which region of the body harbours the least commensal bacteria?
Stomach - 10^4
harsh acidic conditions
What can have a profound effect on composition of gut flora?
DIET
bottle-fed v breast fed
What are some commensal flora of the gut?
Bacteriodes spp.
C. perfringens
E. coli
E. faecalis
What are common BACTERIAL causes of diarrhoea?
Salmonella Shigella E.coli Campylobacter Cholera C. difficile S. aureus B. cereus
What happens during bacterial gastroenteritis?
Enterotoxin production
OR
Aherence
Why is adherence for bacterial gastroenteritis costly in terms of resources
molecular factors are involved
there needs to be control on genetic and transcriptional level to be produced at the right time
Facts about cholera?
Vibrio Cholerae
Rice water stool
transmission - faecal oral route
Who stopped the huge cholera outbreak in Soho London?
John Snow
The cholera toxin?
AB toxin GM1 receptor - internalises toxin in epithelium turns on G proteins ^ cAMP levels release Cl- ions
facts about Salmonella?
comes from contaminated foodstuffs (poultry, eggs)
How does salmonella enter epithelial cells?
bacterial-mediated endocytosis
disrupts tight junctions between intestinal wall cells
membrane is ruffled
Can salmonella cells enter macrophages?
YES
Typhoidal serovars - dissemination
What is the Type 3 secretion system?
Pore complex
Needle
basal body
pumps in effector protein SopB
interact with rogue GTPases
cytoskeletal remodelling
subvert cytoskeleton - membrane ruffles
engulfed
How many salmonella pathogenicity islands harbour genetic loci of the the type 3 secretion system?
2 islands
Who is typhoid Mary?
cook who refused to stop working
asymptomatic carrier of salmonella typhi - resided in the gall bladder
poor hygiene spread to family members who she worked for
How does E.Coli adhere?
Tir protein groups
Intimin binds E.coli to membrane
Tir is polarised to bottom of cell where contact is being made
directed down needles into the cell
What did patients with E.coli O157 develop?
Haemolytic uraemic syndrome (HUS)
How many toxins does C. difficile have
3
Toxin A
Toxin B
Binary toxin
What does C. difficile cause?
Diarrhoea
Toxic megacolon
P. colitis
What does a Phase Bright Spore of C. difficile mean?
Dormant
resistant
What does a Phase Dark Spore of C. difficile means?
Early stage
Germination
What does a Vegetative cell of C. difficile mean?
Proliferation
Toxin Production
What is the activity of TcdA and TcdB in C. difficile?
TcdA - neutrophil infiltration, chemokine production, disruption of tight junctions
apoptosis
INACTIVATE RHO RAC AND GTPASE
- actin condensation
- transcriptional activation
- apoptosis
COMBO = FLUID ACCUMULATION
What post-infectious complications can Campylobacter cause?
reactive arthritis
Guillain-Barré syndrome
IBS
What are 2 types of campylobacter?
C. jejuni
C. coli
What is campylobacter caused by?
uncooked meat
unpasteurised milk
untreated water
What is the mechanism of action of campylobacter?
1/2 flagella
35cfu infective dose
penetration into intestinal mucosa: adhesion, internalisation, translocation
toxin arrests cell division in G2 phase
How is gastroenteritis treated?
AVOID ANTIBIOTICS
prolongs/worsens
except:
- very young/old
- campylobacter
- invasion
