GIT pathogens - Bacteria - Intoxication Flashcards
Staph aureus incubation period
2-6 hours
Bacteria causing intoxication: 1) 2) 3) 4)
1) Staphylococcus aureus
2) Bacillus cereus - emetic type
3) Bacillus cereus - diarrhoeal type
4) Clostridium perfringens
Bacillus cereus emetic type incubation period
1-5 hours.
Bacillus cereus diarrhoeal type incubation period
6-15 hours.
Clostridium perfringens incubation period
6-24 hours.
Staph aureus associated foods
Salty or sugary foods.
Bacillus cereus emetic type associated foods
Rices, pulses
Bacillus cereus diarrhoeal type associated foods
Meat, dried vegetables, milk products, soup.
Clostridium perfringens associated foods
Fish, poultry, beef, sauces, gravy.
Staph aureus toxin type
Heat-stable enterotoxin (types A, B, C, D, E, F, G).
Heat-stable enterotoxin mods of action
Binds neural receptors in upper GIT. Stimulates vomiting centre in the brain.
Bacillus cereus emetic type toxin
Heat-stable cereulide toxin.
Bacillus cereus diarrhoeal type toxin
1)
2)
1) Heat-labile toxin - Haemolysin BL.
2) Enterotoxin Nhe.
Enterotoxin Nhe mode of action
Increase adenylate cyclase concentration.
Increased intestinal fluid secretion.
Clostridium perfringens toxin mode of action.
Inhibits glucose transport in lumen.
Intestinal cells damaged, protein loss to lumen.
Clostridium perfringens pathogenesis
Bacteria sporulate in stomach acid. Sporulation releases toxin.
Staph aureus infective dose
10^5/g of food
Bacillus cereus emetic type infective dose
10^5/g of food. Spores can survive boiling, desporulate with slow cooling.
Bacillus cereus diarrhoeal type infective dose
under 10^5/g of food.
Clostridium perfringens infective dose
10^6/10^7/g of food.
Intoxication
Presence of pre-formed toxin in food. Rapid onset of symptoms.
