19. Food Poisoning Flashcards
What questions should be asked when taking a history of food poisoning?
Onset, duration Travel history, food history Sick contacts Medications that cause diarrhoea Severe: fever, acute abdomen
What investigations can be done into food poisoning?
PCR, selective culture and light microscopy for protozoa on stool
Blood cultures if hospitalised
Which pathogens produce toxins which cause food poisoning?
Staph aureus
Bacillus sereus
Clostridium
How does food become contaminated with staph aureus enterotoxin?
Food handler doesn’t wash hands and food left at room temperature
What are the 2 syndromes caused by bacillus cereus?
Type 1: Emetic syndrome (preformed toxin)
Type 2: Diarrhoeal syndrome (toxin produced in small intestine)
What food is classically contaminated with preformed bacillus cereus toxin?
Boiled rice
What is the aetiology of clostridium perfringens food poisoning?
Classically associated with gravy
Contaminated with heat resistant spores
What is the aetiology of clostridium botulinum food poisoning?
Typically canned food contaminated with toxin
Toxin absorbed from GIT into bloodstream
Blocks ACh release
What bacteria is the most common cause of food poisoning?
Campylobacter jejuni
What is the aetiology of campylobacter food poisoning?
Zoonosis; no person to person spread
Meat carcasses, especially chicken, contaminated with faeces during slaughtering
Increased rates during BBQ season
What is the pathogenesis of campylobacter food poisoning?
Adheres to jejunum and ileum
Cytotoxin causes local damage, occasionally haemorrhagic necrosis
What complications are associated with campylobacter?
Toxic megacolon
BSI
Guillan Barre
What is the gram stain of campylobacter?
Curved gram negative bacillus
What are the lab features of campylobacter?
Oxidase positive
Greyish colonies on charcoal agar
Hydrolyses hippurate
What is the treatment for campylobacter BSI?
Azithromycin or ciprofloxacin
What is the most common serotype of enterohaemorrhagic E.coli?
O147:H7
What complication is associated with enterohaemorrhagic E.coli?
Haemolytic uraemic syndrome
How is e.coli O157 differentiated from other e.coli?
On a mannitol/sorbitol plate, O157 doesn’t ferment sorbitol
What toxins are associated with enterotoxigenic e.coli?
LT and ST toxins
Cause secretion of fluid and electrolytes
What infection is caused by enteropathogenic e.coli?
Infants <6 months in developing countries
Causes severe dehydration
Invasion and loss of villi in small intestine
How is listeria food poisoning contracted?
Milk products, even refrigerated
Vertical transmission
Animal contact
How does listeria evade the immune system?
Survives within macrophages
What are the complications of perinatal listeriosis?
Miscarriage
IU death
Premature labour
Neonatal listeriosis
What are the lab features of listeria?
Gram positive bacillus
Tumbling motility at 25C
What is the treatment for listeria?
High dose amoxicillin and gentamicin
What antibiotic is listeria resistant to?
Cephalosporins
What parasite can contaminate water?
Cryptosporidium parvum
Why are boil water notices given if a water supply is contaminated with cryptosporidium?
Oocytes can survive outside body and can’t be killed with chlorine
How is cryptosporidium detected?
Auramine or PCR
