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Foodborne Infections

By Levi Clancy for Student Reader on

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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


Produces many chemical compounds 12 are psychoactive (ergotamines)