Microorganisms Causing Food Poisoning
Three species of bacteria cause food poisoning via preformed toxin: Clostridium botulinum, Staphylococcus aureus, and Bacillus cereus. Clostridium botulinum is a bacterium that grows in the absence of oxygen and produces one of the most toxic, deadly chemicals known to humans. It was first isolated from sausages, but later was responsible for death in persons consuming home-canned vegetables. The symptoms are flaccid paralysis eighteen to thirty-six hours after ingestion, with respiratory paralysis and death if untreated. There are antitoxins against botulinum toxin, if the type is identified and the antitoxin is injected in time. Botulinum toxin can be inactivated by heating the food to boiling for five minutes. Interestingly enough, botulinum toxin, in spite of its great toxicity is finding a use in eliminating lines and wrinkles from human skin by preventing activity of muscles directly involving those areas of the skin that have wrinkles or expressions. This is partially a response to the fact that very toxic substances in minute quantities can become stimulants. A second serious type of food poisoning is caused by the ingestion of staphylococcal toxin produced by Staphylococcus aureus in foods such as cream puffs, mayonnaise, ice cream, or other nutritious foods that become infected with staphylococci, often carried in the nasal secretions of food handlers. Staphylococcal toxin causes a rather violent nausea and vomiting thirty minutes to six hours after consuming food contaminated with the toxin. Staphylococcus toxin is not inactivated by boiling. It generally is not fatal. Bacillus cereus also produces a food-poisoning toxin. Steamed rice held overnight at room temperature has been a typical food causing Bacillus cereus poisoning. There are two toxins involved—one causing nausea and vomiting, the other causing diarrhea. The toxins are not inactivated by boiling.
Microorganisms Producing Food Poisoning by Toxins Formed in the Intestinal Tract
Clostridium perfringens, an anaerobic microorganism that can cause gangrene in wounds, can also cause food poisoning if it overgrows food materials, such as gravies and meats, which are then consumed. It produces its toxin in the intestinal tract of the consumer and causes diarrhea. Vibrio cholerae is a major cause of cholera in man; it is spread via contaminated water and food. The symptoms are profuse diarrhea, which, if not treated to replace fluids in the body, will lead to death. Vibrio parahemolyticus, found in contaminated shellfish, also leads to profuse diarrhea and requires fluid replacement and antibiotics. Shiga toxin–producing Escherichia coli (STEC), found in contaminated water and meats such as hamburger, is a serious food pathogen leading to hemorrhagic colitis (diarrhea with blood). Bovine products are a major source, but lettuce, alfalfa sprouts, and apple cider have also been implicated. Enterotoxigenic E. coli (ETEC) is frequently found in developing countries in contaminated water and food and is associated with travelers' diarrhea (diarrhea without blood).