19. Food Poisoning Flashcards

1
Q

What questions should be asked when taking a history of food poisoning?

A
Onset, duration
Travel history, food history
Sick contacts
Medications that cause diarrhoea
Severe: fever, acute abdomen
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2
Q

What investigations can be done into food poisoning?

A

PCR, selective culture and light microscopy for protozoa on stool
Blood cultures if hospitalised

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3
Q

Which pathogens produce toxins which cause food poisoning?

A

Staph aureus
Bacillus sereus
Clostridium

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4
Q

How does food become contaminated with staph aureus enterotoxin?

A

Food handler doesn’t wash hands and food left at room temperature

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5
Q

What are the 2 syndromes caused by bacillus cereus?

A

Type 1: Emetic syndrome (preformed toxin)

Type 2: Diarrhoeal syndrome (toxin produced in small intestine)

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6
Q

What food is classically contaminated with preformed bacillus cereus toxin?

A

Boiled rice

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7
Q

What is the aetiology of clostridium perfringens food poisoning?

A

Classically associated with gravy

Contaminated with heat resistant spores

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8
Q

What is the aetiology of clostridium botulinum food poisoning?

A

Typically canned food contaminated with toxin
Toxin absorbed from GIT into bloodstream
Blocks ACh release

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9
Q

What bacteria is the most common cause of food poisoning?

A

Campylobacter jejuni

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10
Q

What is the aetiology of campylobacter food poisoning?

A

Zoonosis; no person to person spread
Meat carcasses, especially chicken, contaminated with faeces during slaughtering
Increased rates during BBQ season

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11
Q

What is the pathogenesis of campylobacter food poisoning?

A

Adheres to jejunum and ileum

Cytotoxin causes local damage, occasionally haemorrhagic necrosis

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12
Q

What complications are associated with campylobacter?

A

Toxic megacolon
BSI
Guillan Barre

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13
Q

What is the gram stain of campylobacter?

A

Curved gram negative bacillus

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14
Q

What are the lab features of campylobacter?

A

Oxidase positive
Greyish colonies on charcoal agar
Hydrolyses hippurate

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15
Q

What is the treatment for campylobacter BSI?

A

Azithromycin or ciprofloxacin

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16
Q

What is the most common serotype of enterohaemorrhagic E.coli?

A

O147:H7

17
Q

What complication is associated with enterohaemorrhagic E.coli?

A

Haemolytic uraemic syndrome

18
Q

How is e.coli O157 differentiated from other e.coli?

A

On a mannitol/sorbitol plate, O157 doesn’t ferment sorbitol

19
Q

What toxins are associated with enterotoxigenic e.coli?

A

LT and ST toxins

Cause secretion of fluid and electrolytes

20
Q

What infection is caused by enteropathogenic e.coli?

A

Infants <6 months in developing countries
Causes severe dehydration
Invasion and loss of villi in small intestine

21
Q

How is listeria food poisoning contracted?

A

Milk products, even refrigerated
Vertical transmission
Animal contact

22
Q

How does listeria evade the immune system?

A

Survives within macrophages

23
Q

What are the complications of perinatal listeriosis?

A

Miscarriage
IU death
Premature labour
Neonatal listeriosis

24
Q

What are the lab features of listeria?

A

Gram positive bacillus

Tumbling motility at 25C

25
Q

What is the treatment for listeria?

A

High dose amoxicillin and gentamicin

26
Q

What antibiotic is listeria resistant to?

A

Cephalosporins

27
Q

What parasite can contaminate water?

A

Cryptosporidium parvum

28
Q

Why are boil water notices given if a water supply is contaminated with cryptosporidium?

A

Oocytes can survive outside body and can’t be killed with chlorine

29
Q

How is cryptosporidium detected?

A

Auramine or PCR