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MICR2220 Medical Bacteriology > L6 - Gastrointestinal Tract Infections > Flashcards

L6 - Gastrointestinal Tract Infections Flashcards

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USMLE® Step 1 flashcards
1
Q

Which region of the body harbours the most commensal bacteria?

A

Colon - 10^11

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2
Q

Which region of the body harbours the least commensal bacteria?

A

Stomach - 10^4

harsh acidic conditions

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3
Q

What can have a profound effect on composition of gut flora?

A

DIET

bottle-fed v breast fed

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4
Q

What are some commensal flora of the gut?

A

Bacteriodes spp.
C. perfringens
E. coli
E. faecalis

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5
Q

What are common BACTERIAL causes of diarrhoea?

A 
Salmonella
Shigella
E.coli
Campylobacter 
Cholera
C. difficile
S. aureus 
B. cereus
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6
Q

What happens during bacterial gastroenteritis?

A

Enterotoxin production

OR

Aherence

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7
Q

Why is adherence for bacterial gastroenteritis costly in terms of resources

A

molecular factors are involved

there needs to be control on genetic and transcriptional level to be produced at the right time

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8
Q

Facts about cholera?

A

Vibrio Cholerae

Rice water stool

transmission - faecal oral route

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9
Q

Who stopped the huge cholera outbreak in Soho London?

A

John Snow

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10
Q

The cholera toxin?

A 
AB toxin 
GM1 receptor - internalises toxin in epithelium 
turns on G proteins
^ cAMP levels 
release Cl- ions
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11
Q

facts about Salmonella?

A

comes from contaminated foodstuffs (poultry, eggs)

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12
Q

How does salmonella enter epithelial cells?

A

bacterial-mediated endocytosis

disrupts tight junctions between intestinal wall cells

membrane is ruffled

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13
Q

Can salmonella cells enter macrophages?

A

YES

Typhoidal serovars - dissemination

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14
Q

What is the Type 3 secretion system?

A

Pore complex
Needle
basal body

pumps in effector protein SopB

interact with rogue GTPases

cytoskeletal remodelling

subvert cytoskeleton - membrane ruffles

engulfed

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15
Q

How many salmonella pathogenicity islands harbour genetic loci of the the type 3 secretion system?

A

2 islands

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16
Q

Who is typhoid Mary?

A

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

17
Q

How does E.Coli adhere?

A

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

18
Q

What did patients with E.coli O157 develop?

A

Haemolytic uraemic syndrome (HUS)

19
Q

How many toxins does C. difficile have

A

3

Toxin A
Toxin B
Binary toxin

20
Q

What does C. difficile cause?

A

Diarrhoea
Toxic megacolon
P. colitis

21
Q

What does a Phase Bright Spore of C. difficile mean?

A

Dormant

resistant

22
Q

What does a Phase Dark Spore of C. difficile means?

A

Early stage

Germination

23
Q

What does a Vegetative cell of C. difficile mean?

A

Proliferation

Toxin Production

24
Q

What is the activity of TcdA and TcdB in C. difficile?

A

TcdA - neutrophil infiltration, chemokine production, disruption of tight junctions
apoptosis

INACTIVATE RHO RAC AND GTPASE

  • actin condensation
  • transcriptional activation
  • apoptosis

COMBO = FLUID ACCUMULATION

25
Q

What post-infectious complications can Campylobacter cause?

A

reactive arthritis
Guillain-Barré syndrome
IBS

26
Q

What are 2 types of campylobacter?

A

C. jejuni

C. coli

27
Q

What is campylobacter caused by?

A

uncooked meat
unpasteurised milk
untreated water

28
Q

What is the mechanism of action of campylobacter?

A

1/2 flagella
35cfu infective dose

penetration into intestinal mucosa: adhesion, internalisation, translocation

toxin arrests cell division in G2 phase

29
Q

How is gastroenteritis treated?

A

AVOID ANTIBIOTICS
prolongs/worsens

except:

  • very young/old
  • campylobacter
  • invasion

MICR2220 Medical Bacteriology (16 decks)

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