Escherichia coli are healthy, rod-shaped, bacterial flora that populate the human digestive system within hours of birth. In 1885, German pediatrician Thomas Escherichia isolated the bacteria in the colons of newborns. These healthy bacteria suppress the growth of harmful bacteria and produce vitamin K and B-complex vitamins. But some strains of the bacteria contain damaged DNA, and do far more harm than good, leaving humans to deal with the Jekyll and Hyde of the bacteria world. Green onions are particularly susceptible to E. coli and other bacteria because they are typically eaten raw, and are not exposed to heat that might otherwise kill the bacteria.
Mr. Hyde: O157
There are many strains of this bacteria, though the one responsible for contamination in green onions and most other food products is O157:H7. Long ago, this strain was infected by a virus that altered its DNA. Because E. coli reproduces by cell division, each time the infected cell divided, the mutated DNA went with it to all subsequent cell divisions. It produces a toxin, called shiga-like toxin, which damages the lining of the digestive system in humans, causing enterohemorrhagic disorder, or internal bleeding, and can lead to a type of kidney failure called hemolytic uremic syndrome.
Contamination Sources
Green onions become contaminated when they are exposed to water that contains animal or human waste. This can occur if growers are not vigilant about irrigation practices, or when meat or dairy is processed near the farm where the onions are grown. In fact, cattle have been identified as the most common carrier of E.coli. A 2002 study by the U.S. Department of Agriculture revealed that 38.5 percent of U.S. dairy farms had at least one cow that tested positive for E. coli. Unsafe handling -- preparing food with unwashed hands, or using cooking or serving utensils that have been exposed to affected foods --- could also result in contamination. Other raw foods, as well as dairy products, mayonnaise, improperly stored or heated frozen foods and undercooked meats are also vulnerable to E. coli. Community water supplies can also be a source of contamination; careful monitoring and testing are imperative.
Green Onions Contamination
In recent years, E. coli has contaminated many foods including green onions, ground beef, spinach, tomatoes and prepackaged, refrigerated cookie dough. In December 2006, E. coli O157:H7 was associated with green onions from Taco Bell restaurants in the eastern U. S. These tiny bulbs seem to have taken a hit because they are typically eaten raw; since 2000, they have carried not only E. coli, but also salmonella and hepatitis A. A March 2011 alert from the U. S. Department of Health and Human Services stated that three farms in Mexico were "red listed," or subject to having their shipments of green onions and other root vegetables refused due to poor sanitation practices.
Symptoms and Treatment
Symptoms of E. coli infection include stomach cramps, gas, fever, loss of appetite, vomiting, bruising, bloody urine and pale skin. Most people improve in one to three days without medical attention. If your symptoms worsen, or if you experience significant blood loss or dehydration, seek medical attention. Avoid medications that stop diarrhea as they may retain the bacteria in the digestive tract and prolong illness. Hydrate with electrolytes to balance body fluids.
Prevention
To prevent food poisoning from E. coli and other bacteria, always wash your hands after using the restroom since E. coli is eliminated in waste. Before eating green onions and other raw foods, rinse them carefully. Separate raw and cooked foods, as well as the cooking utensils and serving dishes used for raw and cooked foods. The USDA recommends cooking meat thoroughly to prevent E. coli contamination. Fully cook frozen foods too, and refrigerate leftovers quickly. Avoid drinking untreated water. The USDA continues to monitor sanitation procedures for raw produce to prevent contamination.
References
- University of Kansas; Department of Molecular Biology; What the Heck is an E. Coli? John C. Brown; September 1997
- MedlinePlus: E. Coli Enteritis
- Food and Drug Administration: Safety: Recall; August 2009
- Centers for Disease Control and Prevention; Multistate Outbreak of E. coli O157 Infections, November-December 2006; December 2008
- U. S. Department of Health and Human Services; Detention Without Physical Examination of Green Onions (Scallions) from Specific Firms in Mexico; March 2011
- University of Wisconsin-Madison; School of Veterinary Medicine; E. coli O157:H7 and Salmonella Typhimurium DT104: The Role of Animals; Christopher W. Olsen; 2004
