Special to CNN.com
Eating unwashed produce, such as spinach, lettuce or green onions, or undercooked beef, especially hamburger, can increase your risk of infection with Escherichia coli (E. coli) bacteria. E. coli are a broad group of bacteria that live in the intestinal tract of healthy people and animals. Most of the bacteria are harmless and play an essential role in absorbing certain vitamins. But a few strains of E. coli are responsible for serious food-borne infections.
A particularly virulent strain of E.coli, called E. coli O157:H7, can cause severe, bloody diarrhea, kidney failure and even death. Most cases of E. coli O157:H7 have been traced to undercooked ground meat, but the bacteria can also contaminate raw fruits, particularly melons, and vegetables, such as lettuce, sprouts, tomatoes, spinach and green onions. Prepackaged vegetables and salad mixes may present a particular risk. Although it's not always possible to prevent food poisoning, knowing how E. coli spreads and how to handle food safely can help you avoid getting sick.
Dissecting the bad bugs
Not all disease-causing E. coli bacteria are created equal. One strain, enterotoxigenic E.coli, is a leading cause of diarrhea in children in developing nations. It's also responsible for most cases of traveler's diarrhea and is an increasing source of food-borne infection in industrialized countries.
Enterotoxigenic E.coli bacteria spread in contaminated food — including raw fruits and vegetables, raw seafood, and unpasteurized dairy products — and in contaminated water. Signs and symptoms, which include watery diarrhea and abdominal cramping, usually last just a few days. The infection normally clears on its own without treatment, and most adults and children have no lasting ill effects.
But E. coli O157:H7 is different. It produces a toxin that damages the lining of the small intestine, leading to intense abdominal cramps and severe, bloody diarrhea. You may have 10 or more bowel movements a day, some consisting almost entirely of blood. The marked loss of fluids and electrolytes causes dehydration and fatigue.
Nevertheless, many people recover completely from the infection in five to 10 days. But others, especially older adults, children under the age of 5 and people with weakened immune systems, may develop a serious complication called hemolytic uremic syndrome. This syndrome damages the lining of the tiny blood vessels in the kidneys, sometimes leading to kidney failure.
Even with the best of care, including blood and platelet transfusions and kidney dialysis, a few children die every year of hemolytic uremic syndrome. Others may have lifelong kidney problems or require long-term dialysis. Still others develop further complications such as high blood pressure, seizures, blindness and paralysis.
How E. coli spreads
You develop an E. coli infection when you accidentally ingest the bacteria. These are the most common sources of infection:
* Contaminated food. E. coli bacteria exist naturally in the intestine of many animals, including cattle. Meat can become contaminated with fecal matter containing the bacteria when cattle are slaughtered or processed. The problem is particularly serious in modern feedlots, where animals spend their lives in crowded, filthy conditions. Although beef in general may be contaminated, ground meat is a special concern because grinding combines meat from different animals and transfers bacteria from the meat's surface to its interior. The bacteria also can spread from one surface to another, which means that bacteria on a cow's udder or on equipment can end up in milk. Pasteurization kills the bacteria, but raw milk can be a source of infection. Other foods that may become contaminated with the bacteria include dry cured sausage, salami, alfalfa sprouts, lettuce, and unpasteurized apple juice and apple cider.
* Contaminated water. Runoff from feedlots can contaminate ground and surface water, including water used to irrigate crops. Drinking or inadvertently swallowing untreated water from lakes and streams can cause infection. So can eating unwashed raw fruits and vegetables. And although public water systems use chlorine, ultraviolet light or ozone to kill E. coli, some outbreaks have been linked to contaminated municipal water supplies. Private wells are a greater cause for concern. If you have a private well, have it tested once a year for pathogens, including E. coli. Your state health department can help you find a laboratory certified to conduct the tests.
* Person-to-person contact. E. coli bacteria can easily travel from person to person, especially when infected adults and children don't wash their hands properly. Family members of young children with the infection are especially likely to become sick themselves. Children can shed the bacteria in their stools for up to two weeks after symptoms improve.
Keeping E. coli at bay
It's not always possible to avoid food poisoning, but common-sense precautions can go a long way toward preventing infection with E. coli O157:H7 bacteria.
* Cook all ground meat, hamburger or roast beef thoroughly. Meat, especially if grilled, is likely to brown before it's completely cooked, so use a meat thermometer to ensure that meat is heated to at least 160 F at its thickest point. If you don't have a thermometer, cook ground meat until no pink shows in the center.
* To prevent the growth of bacteria in your kitchen, thoroughly wash anything that comes in contact with raw meat, including your hands, counters and utensils. Use hot, soapy water, bleach or disinfecting wipes. Never put cooked hamburgers on the same plate you used for raw patties.
* Order beef cooked medium or well-done when eating out. Be persistent about getting what you ask for, even if it means sending your food back more than once.
* Drink pasteurized milk, juice and cider. Any boxed or bottled juice kept at room temperature is likely to be pasteurized, even if the label doesn't say so.
* Wash raw produce thoroughly, using plenty of running water and a scrub brush or a vegetable wash. Children, older adults and people with weakened immune systems should avoid alfalfa sprouts.
* Avoid drinking untreated water from lakes and streams and swallowing water when swimming — even pool water, which can be contaminated with feces.
* Make sure that family members, including children, wash their hands after using the bathroom, changing diapers and before eating.
You're sick: Now what?
Most E. coli infections — even those caused by E. coli O157:H7 — aren't life-threatening. But the bacteria can cause serious and even fatal illness in some people. If you're at high risk of hemolytic uremic syndrome, see your doctor at the first sign of profuse or bloody diarrhea. If you're not at risk, seek medical advice if your symptoms are severe or persistent. You should have your stool checked for E. coli bacteria.
Most cases of traveler's diarrhea clear up on their own in a few days, although doctors sometimes prescribe a short course of the antibiotic rifaximin (Xifaxan), which reduces the number of E. coli bacteria in the gut. When it comes to more severe infections such as O157:H7, however, no current treatments can cure the infection, relieve symptoms or prevent complications.
Anti-diarrheals can make O157:H7 worse by preventing your body from eliminating the toxins. And antibiotics increase the risk of hemolytic uremic poisoning. For most people with O157:H7 infection, rest and plenty of fluids to prevent dehydration are the best option.
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December 11, 2006
Tuesday, March 25, 2008