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Clinical Pathology - > CP23 - Gastroenteritis > Flashcards

CP23 - Gastroenteritis Flashcards

1
Q

what are facultative organisms?

A

those that can grow in both aerobic and anaerobic conditions

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2
Q

what are the benefits of gut flora?

A

metabolism
colonisation resistance for other bacteria
antibody induction eg. during allergies

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3
Q

what factors affect the flora present in the gut?

A

diet

breast/bottle feeding

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4
Q

what is the common flora found in the gut?

A
  1. bactericides
  2. prevotella
  3. Clostridia
  4. Bifidobacteria
  5. enterobacteriacea
  6. enterococci
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5
Q

why are a lot of GI diseases associated with travel?

A

putting your normal gut flora in a different environment and having them encounter different substances can cause problems

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6
Q

what are the common mechanisms through which bacteria cause gastroenteritis?

A
  1. endotoxin production

2. Adherence

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7
Q

which bacteria cause gastroenteritis by endotoxin production?

A

vibrio cholera - sporadic cases seen in returning travellers
E. coli
C. diff
Staph aureus - food poisoning
Bacillus cereus - spores can survive cooking. food poisoning can occur when meat cooked in advance and kept warm
C. perfringens

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8
Q

which bacteria cause gastroenteritis by adherence?

A

shigella Sonnei and shigella flexneri - bacillary dysentry
E. coli
Campylobacter jejune -undercooked meat, both toxin and adherence
salmonellae - food poisoning, typhoid, paratyphoid

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9
Q

what is bacillary dysentry?

A

infection of the intestines resulting in severe diarrhoea with the presence of blood and mucous in the faeces

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10
Q

what is typhoid?

A

an infectious bacterial fever with an eruption of red spots on the chest and abdomen and severe intestinal irritation

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11
Q

what is paratyphoid?

A

a fever resembling typhoid but caused by different but related bacteria

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12
Q

what are the parasitic causes of gastroenteritis?

A

entamoeba
G. lambia
cryptosporidium

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13
Q

what are the viral causes of gastroenteritis?

A

norovirus

rotavirus

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14
Q

what is the epidemiology of gastroenteritis?

A

food borne diseases have reduced while non food borne diseases have increases in prevalence

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15
Q

how does gastroenteritis present?

A

acute onset
D&V - ask for frequency, mucous, blood
abdo pain
systemic effects - fever etc.
other complications - dehydration, renal failure, haemolytic uraemia syndrome, toxic megacolon, Guillain-Barre syndrome, salmonella

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16
Q

what facts are important to ask for if gastroenteritis is suspected?

A 
travel history
food history
any unwell people they may be in contact with
immunotherapy
blood in stool
17
Q

how long does a GI infection last for in an otherwise healthy patient?

A

24 hours

18
Q

what investigations need to be done if a GI infection is suspected?

A

bloods - FBC, U&Es, CRP, cultures - only for disseminated infections
creatinine - a marker of infection
AXR if severe
assess stool for ova, parasites and cysts, microscopy

19
Q

what is viral gastroenteritis also called?

A

winter vomiting disease - caused by norovirus. common

20
Q

what are the symptoms of viral gastroenteritis?

A

diarrhoea, projectile vomiting

21
Q

how long does viral gastroenteritis last?

A

24-48 hours

22
Q

how is viral gastroenteritis usually managed?

A 
no specific treatment
infection allowed to follow its course
lots of water to prevent dehydration
good hygiene to prevent spread
it is rarely dangerous
23
Q

what is cryptosporidiosis?

A

cryptosporidium infection
predominantly waterborne, because oocysts are resistant to chlorine based disinfectants like those found in swimming pools

24
Q

what are the effects of cryptosporidiosis on the body?

A

watery diarrhoea, mild to severe disease. most commonly in young children
no specific treatment

25
Q

what is the main virulence factor of E. coli?

A

shiga toxin

26
Q

what are the effects of shiga toxin?

A

premature destruction of RBCs, and these can then clog kidneys, causing haemolytic-uraemia syndrome

27
Q

what is the main species that produces shiga toxin?

A

shigella

28
Q

what is the mechanism of shiga toxin action?

A
  1. activates g protein leading to increased levels of cAMP
  2. activates ion channels
  3. cells over-excrete chloride ions
  4. water follows ions out of cells into the bowel
  5. this can be up to 6L a day, rapid dehydration results
29
Q

what is the direct result of efflux of K or Cl ions from cells?

A

diarrhoea

30
Q

what are the 2 types of salmonella?

A

typhoidal - can disseminate

non-typhoidal - cannot disseminate

31
Q

how is gastroenteritis treated?

A
  1. supportive management
  2. avoid antibiotics, because they may increase the duration of salmonella carriage or may worsen HUS caused by E. coli
  3. point 2 to be ignored if patient is at an extreme age, if the infection is caused by campylobacter
    or if the patient becomes septic
32
Q

what is antibiotic diarrhoea?

A

diarrhoea cause due to disruption of gut flora by antibiotics
symptoms could range from mild diarrhoea to pseudomembranous colitis (toxic megacolon, perforation, shock)
c diff infection can cause pseudomembranous colitis plaques

33
Q

what are the risk factors for c diff diarrhoea?

A

old age and primary illness

34
Q

which antibiotics put you at a high risk for C diff?

A

generally, the broader the spectrum,the greater the risk
cephalosporins
clindamycin

35
Q

which antibiotics put you at a medium risk of c diff?

A 
ampicillin
amoxicillin
co-trimoxazole
macrolides
fluoroquinolones
36
Q

which antibiotics put you at a low risk of c diff?

A 
ahminoglycosides
metronidazole
anti-psudomonal penicillins
tetracyclines
rifampicin
vancomycin
37
Q

how are c diff infections treated?

A

antibiotics - oral metronidazole or vancomycin

faecal transplant - either faecal or oral route

38
Q

what are the benefits of faecal transplants?

A

c diff cycle is broken by repairing the problems with the gut flora
increasing the diversity of the microflora in the patient’s gut

Clinical Pathology - (15 decks)

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