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Gastrointestinal Infections Flashcards

1
Q

Ulceration of mucosal epithelium can lead to what?

A

Perforation. May result in leaking of food & gastric juices to peritoneum/abdominal cavities. Requires surgery

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2
Q

What varies across bacterial diarrhoea?

A

incubation period
duration of diarrhoea
symptoms

Shigella, Campylobacter

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3
Q

Vibrio Cholera
Gram ______
What shape?
Virulence factors (X3)

A

negative
comma shaped rod
flagella, mucinase, toxin

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4
Q

Describe the toxicity of vibrio cholera

A

produces toxin: subunit A and B (x5) which binds to cell surface receptor GM1 –> endocytosed –> increase in secretagogue cAMP –> lose loads of Cl- ions and fluid loss

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5
Q

What happens in cholera-induced fluid loss from infection?

A

fluid and electrolyte loss causes dehydration, hypokalaemia, metabolic acidosis

HYPOVOLAEMIC SHOCK
40-60% mortality

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6
Q

E.Coli
Gram _____
Shape?

A

negative

bacillus

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7
Q

EPEC

A

enteropathogenic: sporadic cases, outbreaks in infections in U5s

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8
Q

ETEC

A

enterotoxigenic: traveller’s diarrhoea

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9
Q

VTEC

A

verocytotoxin-producing: sporadic and cases of gastroenteritis

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10
Q

EIEC

A

entero-invasive

food-borne infection in areas of poor hygiene

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11
Q

EAEC

A

enteroaggregative

resource-poor countries

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12
Q

Two mechanisms E.coli use to effectively adhere

A
  1. pili

2. pedestal formation (part of lesion and outs itself in middle of it)

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13
Q

Two modes of action of ETEC E.coli

A

enterotoxin
1. heat labile (increased cAMP)
2. heat stable (increased cGMP)
both lead to huge fluid loss

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14
Q

Campylobacter jejuni (most common diarrhoea!!)
Gram ____
Shape?
Transmission through what?

A

negative
helical bacillus
consumption of raw/undercooked meat, contaminated milk

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15
Q

C/jejuni infection histological appearance

A

inflammation involves ENTIRE mucosa
villous atrophy
necrotic debris in crypts
thickening of basement membrane

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16
Q 
Salmonella spp. 
Gram \_\_\_
Shape? 
Transmission?
2 examples
A

negative
bacilli
food-associated diarrhoea, transmitting through consumption of raw/undercooked meat, contaminated eggs and milk

eg. Salmonella typhi and salmonella paratyphi

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17
Q

Pathogenesis of Salmonella infection

A

have to eat lots of it
absorb onto epithelial cells of small intestine
penetrate and migrate to lamina propria
multiply on lymphoid follicles (Peyer’s patches)
inflammatory response –> prostaglandins
stimulate cAMP
fluid and electrolyte loss

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18
Q

S.typhi and S.paratyphi cause what fevers?

How do they multiply and transport?

A

Enteric: typhoid fever and paratyphoid

in macrophages

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19
Q

Diarrhoea, Rosa spots

A

SUGGESTS TYPHOID FEVER FROM SALMONELLA!!

notifiable disease - must report it legally to public health

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20
Q

Where can salmonella hide?

A

in the gallbladder - can be chronic! think typhoid mary

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21
Q

Shigella
Shape?
Most common species? (which causes what)

A

Bacillus
Cause shigellosis (dysentery)
Most common is S.dysenteriae

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22
Q

Pathogenesis of Shigella

A

attaches to mucosal epithelium of distal ileum and colon
inflammation and ulceration
produces Shiga TOXIN
watery diarrhoea, blood and mucus

23
Q

What foods might a pregnant woman/immunosuppressed be advised to avoid for Listeria monocytogenes?

A

Pate
soft cheese
unpasteurised milk
houmous

24
Q

How does listeria monocytogenes usually present?

A

as meningitis

25
What is antibiotic-associated diarrhoea?
doesn't involve ingestion of pathogen or a toxin! if we take antibiotics for bug X, it can also wipe out nice gut microbiota. disruption of the homeostasis in the gut microbiota.
26
Virulence factors of C.Diff?
spores toxins: enterotoxin and a cytotoxin nosocomial (healthcare setting-acquired)
27
What is clever about clostridium perfringens?
``` animal products (eat raw meat) and soil (unwashed veg) SPORES: survive cooking and germination takes place avoids acid in stomach too ``` damages intestinal epithelium and cause diarrhoea
28
Why is rotavirus clever?
has 11 separate segments of ds-RNA so can adapt and vary. (influenze virus does this too) very small infective dose (10 ingested particles - very effective transmission!)
29
what weather most likely to develop rotavirus?
cooler months
30
transmission of rotavirus
faecal-oral, can be faecal-respiratory
31
Rotavirus vaccine
first dose at age 6-10 weeks live, attenuated virus in US, hospital admissions decreased by 86%
32
Norovirus transmission? why so infectious? vaccine?
faecal-oral contaminated water associated with projectile vomiting (highly infectious!!) no vaccine (wash hands)
33
3 gastrointestinal protozoal infections
Giardia Lamblia Cryptosporidium parvum Entamoeba histolytica
34
Giardia lamblia infective dose transmission
traveller's diarrhoea small infective dose drinking water and recreational water
35
Lifecycle of G.lamblia
2 stages 1. Trophozoite: bi-nucleated and has flagella. Lives in the upper SI and adheres to the brush border of epithelial cells. 2. Cyst: the bit that's excreted. encased and resistant to environment.
36
Pathogenesis of G.lamblia What's the two-fold damage?
works its way from gut to gallbladder. attaches to mucosa via ventral sucker (doesn't PENETRATE epithelial cells but still causes damage to mucosa and villous atrophy) 1. fluid loss 2. villous atrophy causes failing to absorb things
37
Cryptosporidium parvum
oppurtunistic infection associated with AIDS transmission through faecally-contaminated drinking water animal reservoir** VERY infective: 10 oocysts
38
Lifecycle of Cryptosporidium parvum
Has asexual and sexual development in the host Oocyst is ingested in dirty water. Release of sporozoites (invade microvillus and attach to brush border = infective stage) Sporozoites STAY in the body and form merozoites and self-infect OR produce other oocyst excreted
39
Cryptosporidium parvum relevance to HIV
In HIV + individuals with v low CD4+ T cell counts of <100mm, diarrhoea is prolonged and may become irreversible and life-threatening
40
Enteramoeba histolytica transmission what does it do
ingestion of contaminated food/water, anal sexual activity cysts pass through stomach and excyst in SI. adhere to epithelial cells and cause damage via cytolysis. produce enzymes (hydrolytic, proteinases, collagenase, elastase. After mucosal invasion: cysts invade RBCs --> amoebic colitis VERY INVASIVE!!
41
Clinical manifestations of Enteramoeba histolytica
small localised superficial ulcers --> mild diarrhoea | entire colonic mucosa may become deeply ulcerated = severe amoebic dysentery
42
complications of Enteramoeba histolytica
intestinal perforation trophozoites may spread to liver, other organs rarely abscesses can spread to overlying skin
43
3 categories of helminths (which one is most clinically important)
roundworms (nematodes) - MOST CLINICALLY IMPORTANT tapeworms (cestodes) flukes (trematodes)
44
2 ways of infecting roundworms (nematodes)
- swallowing infective eggs | - active skin penetration by larvae and systemic migration through lung to tissue
45
How do you diagnose roundworms (nematodes)
stool microscopy
46
Stronglycoides stercoralis
known as pinworm villous atrophy loss of elasticity of small intestinal wall = bad as lose peristalisis (required to get bugs out)
47
Clinical manifestations in Strongyloides stercoralis
``` dysentery (persistent in immunocompromised) dehydration malabsorption syndrome anal pruritis (itchy bum) associated with appendicitis ```
48
Trichuris trichiura
whipworm can live for 3+ years acquired through eating eggs on veg 10,000 eggs produced daily
49
Ascaris lumbricoides
GIANT roundworm large thick white worm 20-30cm lies dormant for a couple months then starts producing 20,000 eggs a day
50
clinical manifestations of Ascaris lumbricoides
``` allergic reaction digestive upsets protein/energy malnutrition intestinal blockage** worm may invade mouth, nose ```
51
Enterobius vermicularis
threadworm small <1cm female migrates to anus at night to lay 10,000 eggs. develops to infective stage within hours intense itching, secondary infection
52
Ancyclostoma duodenale
little man hookworm walking barefoot in infected areas attaches to SI with mouth, suck blood and protein. HUGE numbers cause hypochromic anaemia lose blood 0.03ml/day/worm (500-1000 worms)
53
Taenia solium
scolex (like hooks on velcro) ingesting worms or eggs in undercooked pork 7m long!!!!!!!!
54
Oral Rehydration Therapy What does it do? Ingredients
replacement of fluids and electrolytes lost during diarrheal illness increases resorption of fluids and salts into intestinal wall glucose NaCl KCl trisodium citrate dihydrate

GI (9 decks)

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