E. coli

Definition
Escherichia coli (E. coli) is a type of bacteria commonly found in the colon of humans and animals. There are many strains of E. coli, most of which are harmless. However, a few strains produce toxins that may cause intestinal infections. One strain, E. coli O157:H7, can cause severe illness.

Strains of E. coli
E. coli infections have been identified in many parts of the world and are a common cause of travelers' diarrhea, persistent diarrhea and childhood diarrhea, especially in developing countries. In 1982, a particularly toxic strain, E. coli O157:H7, was identified in the United States. Since then, E. coli O157:H7 infections have become increasingly common. Its toxins can damage the lining of the intestines, producing bloody diarrhea. In a few children and older adults, the infection destroys red blood cells and causes bleeding and kidney failure. This strain of E. coli can be found in the intestines of healthy cattle or deer and infected humans. You may have heard about this type in the news in association with undercooked ground beef.

Transmission
E. coli O157:H7 is sometimes found in the digestive systems of dairy and beef cattle. From there, the bacteria can contaminate milk, or meat can become infected during the slaughtering process. You can contract E. coli by eating meat (especially ground beef) that is not thoroughly cooked or drinking unpasteurized milk or juice. Specifically, E. coli outbreaks have been linked to unpasteurized apple cider made with apples contaminated by cow manure. E. coli O157:H7 has also been found in cheese products, sprouts, lettuce and salami. Infection can also occur from swimming in sewage-contaminated water or drinking water contaminated with sewage.
E. coli O157:H7 can spread from person to person, especially from children in diapers. Here's how it happens. E. coli leaves the body through bowel movements of a person. If you put anything contaminated with infected stool into your mouth (such as hands, food, toys or other objects), you may contract the infection. The bacteria spread easily when people don't wash their hands after using the toilet or changing diapers. The bacteria are present in the stool of young children for up to 2 weeks after the symptoms of infection have ended.

The incubation period (the time between exposure and appearance of symptoms, if they appear at all) of E. coli O157:H7 is usually three to four days, but it can be as many as eight days.


Signs/symptoms
Some people have no symptoms. For others, common symptoms include sudden abdominal cramping and severe diarrhea that often becomes bloody. Less often, there may be vomiting or mild fever.

Diagnosis
The symptoms of E. coli O157:H7 are similar to other illnesses. To confirm the diagnosis, your doctor will test a stool sample. E. coli O157:H7 requires specialized diagnostic testing because it's not identified through the routine tests done in most labs.

Treatment
Diarrhea caused by E. coli usually goes away on its own after a few days, and other symptoms typically resolve within five to 10 days. Don't take antidiarrhea medication because it slows the elimination of the bacteria from your body. Antibiotics are often not needed to treat E. coli O157:H7. They haven't been found to shorten the diarrhea, and it's unclear whether they decrease or possibly even increase the risk of complications.
If you have diarrhea or are vomiting, drink plenty of fluids to prevent dehydration. In severe cases, intravenous fluid therapy may be needed.

The bacteria may be present in your stool for up to two weeks after symptoms of the infection disappear. If you're infected, don't handle food or provide child or other personal care until all symptoms disappear and your doctor tells you the bacteria have left your system. If you work in the food, health or child care industry, notify your employer of your condition. When you return to your normal diet, start with liquids and then move to bland food. Progress slowly to normal foods.


Complications
If the symptoms are severe, dehydration and electrolyte imbalances may occur. If left untreated, these complications can ultimately be life-threatening. Those at the greatest risk for dehydration include infants and young children; older adults; people who have diabetes, AIDS or cancer; and those who are undergoing chemotherapy or have weak immune systems.
E. coli O157:H7 produces a strong toxin that can cause hemolytic uremic syndrome (HUS) or a condition affecting the number of blood platelets known as thrombotic thrombocytopenic purpura (TTP). About one-third of people who develop HUS have either acute or chronic abnormal kidney function that may require dialysis. The accompanying destruction of red blood cells may require blood transfusions. Other serious complications can be fatal. Children under age 5 and elderly adults are the most likely to contract HUS, which is also the principal cause of acute kidney failure in children.


Pregnancy-specific information
Pregnancy is not a risk factor for E. coli O157:H7 infection.

Senior-specific information
As you age, your natural defenses against food-borne bacteria diminish. Protective stomach acid secretion decreases and the immune system weakens. Elderly adults also have a higher risk of developing complications.

Prevention
You can't tell if food is contaminated with E. coli by sight or smell. Here are some tips to help prevent the spread of E. coli O157:H7 infection:
Cook: Cook to proper temperatures.
Because E. coli can survive refrigerator and freezer temperatures, thorough cooking is the only way to destroy the bacteria. Ground beef should never be eaten rare. The inside of the meat should be gray or brown -- not pink -- and the juices should run clear. Cook the meat to an internal temperature of at least 160°F. It's best to check with a thermometer since recent studies have shown that ground beef sometimes turns brown before it reaches 160° F. If you're eating in a restaurant and receive an undercooked hamburger or other type of meat, send it back for more cooking. It's also a good idea to ask for a clean plate and a new bun.

Separate: Don't cross-contaminate.
Bacteria can spread from one food to another, especially from raw meat, poultry and seafood. Avoid this by keeping these foods away from other foods during shopping, storage and preparation. Use a separate cutting board for meat, poultry and seafood. When you serve cooked food, do not use unwashed dishes or utensils that were used to handle raw foods.

Clean: Wash your hands and kitchen surfaces often.
Wash your hands for at least 20 seconds with hot soapy water before food preparation and after handling raw meat, fish, seafood, eggs or poultry. Also wash your hands after using the toilet, changing diapers, or handling pets. Wash countertops, cutting boards and utensils with hot, soapy water before and after preparing each food. Wash dishcloths and sponges frequently in hot water or use paper towels.

Additional recommendations


Do not drink unpasteurized milk, juice or cider.
Wash fruits and vegetables thoroughly before eating.
Elderly adults, those who have weak immune systems and children under age 5 should avoid alfalfa sprouts.
Drink water that has been treated with adequate levels of chlorine or other disinfectants.
Avoid swallowing water while swimming.
Do not share bath water or swim with someone who has an E. coli infection.
On the research front
Researchers at the National Institute of Child Health and Human Development have developed an experimental vaccine against E. coli O157:H7. In clinical trials, the vaccine caused volunteers to produce enough antibodies (compounds that help neutralize or destroy foreign substances in the blood) to kill the bacteria in lab cultures without serious side effects. Researchers are studying mass vaccination of cattle to eliminate this strain of E. coli.

Irradiation (the therapeutic use of certain types of radiation) can destroy or limit bacteria in food, especially in solid food and animal products. Federal officials estimate that irradiation could eliminate a significant percent of the illness-causing bacteria in our food. The food's nutritional value after irradiation depends on the radiation dose, type of food, packaging and processing conditions (such as temperature during irradiation and storage time). Protein, carbohydrates and fat are fairly stable under irradiation, but vitamins may be more sensitive. Irradiation is practiced in more than 40 countries, but its current use in the United States is governed by strict regulations.