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Foodborne InfectionsComments

Foodborne Infections

Salmonella spp.
  • S. thyphimurium is usual cause of human salmonellosis
  • Gram negative, motile rods, non-sporeforming
  • common in the intestinal tract of fowl
  • produce enteroendotoxins
  • Salmonella spp. found in poultry, eggs, cantaloupe, tomatoes, cilantro, alfalfa sprouts, clover sprouts, mung-bean sprouts, orange juice
S. thyphimurium
  • approx. 10,000 cells are sufficient to cause an infection
  • salmonellosis arises after cells have grown in the intestine
  • symptoms include sudden onset of headache, chills, vomiting, and diarrhea, and a subsequent fever
Escherichia coli O157:H7
  • VTEC strain; i.e., verocytotoxic E. coli
  • also EHEC; i.e., enterohemorrhagic E. coli
  • over half of the cases of infection in the U.S. result from tainted meat
  • a dirty cow's coat contacts the meat during skinning, or fecal matter from the intestines contacts the meat during evisceration
  • also raw fruit juice, unwashed lettuce
  • incubation period of 1-3 days after ingestion
  • cases usually present as diarrhea, possibly with severe abdominal cramps
  • sometimes only mild diarrhea, or no symptoms
  • more serious cases lead to low platelet count and renal failure (HUS ' hemolytic uremic syndrome)
  • bacteria adhere to intestinal mucosa and secrete verocytotoxin
  • toxin cleaves the 28S rRNA of the 60S ribosomal subunit (stops protein synthesis)
  • damages cells of lower intestine reduces ability to absorb fluid (if blood vessels are damaged, this also results in bloody diarrhea)
Staphlococcus aureus
  • most common type of food poisoning
  • Gram positive
  • produces six enterotoxins, which are heat stable
  • can cause diarrhea, vomiting, and nausea, generally within six hours of ingestion
  • S. aureus is often the food poisoning culprit in unrefrigerated mayo, meat, poultry, cream-filled baked goods, etc.
Clostridium botulinum
  • Gram positive, anaerobic, spore-forming
  • lives in soil or water
  • spores may contaminate food (or livestock) before harvest (or slaughter)
  • if correctly processed (to kill spores), no problem
  • however, if spores germinate (initiate growth), even a tiny amount of the toxin can be highly poisonous
  • botulism is very severe... often fatal
  • neurotoxin paralyzes breathing
  • heat labile 80°C for 10 min. destroys toxin
  • poisoning usually occurs in foods that are not cooked after processing
  • smoked meats, canned beans or vegetables, sushi
ErgotProduces many chemical compounds 12 are psychoactive (ergotamines)