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What is E. coli?

Escherichia coli (E. coli) is a bacterium that commonly lives in the intestines of people and animals. There are many strains (types) of E. coli. Most of the E. coli are normal inhabitants of the small intestine and colon and are non-pathogenic, meaning they do not cause disease in the intestines. Nevertheless, these non-pathogenic E. coli can cause disease if they spread outside of the intestines, for example, into the urinary tract (where they cause bladder or kidney infections) or into the blood stream (sepsis).Some strains of E. coli are pathogenic, meaning they can cause disease in the small intestine and colon. These pathogenic strains of E. coli may cause diarrhea by producing and releasing toxins (called enterotoxigenic E. coli or ETEC) that cause the intestine to secrete fluid or by invading and inflaming the lining of the small intestine and the colon (called enteropathogenic E. coli or EPEC). A third strain of E. coli has a tendency to cause inflammation of the colon and bloody diarrhea (called enterohemorrhagic E. coli or EHEC).

What is E. coli 0157:H7?

E coli O157:H7 is a strain of EHEC. It causes colitis and bloody diarrhea by producing a toxin called Shiga toxin, which damages the intestines. E. coli 0157:H7 is a major health problem. It is estimated to cause infection in more than 70,000 patients a year in the United States. It has been reported to cause both large outbreaks as well as isolated sporadic infections in small numbers of individuals. This diarrheal illness was first recognized when the Centers for Disease Control (CDC) isolated E. coli O157:H7 from patients in two separate outbreaks in Oregon and Michigan. The illness was associated with eating hamburgers at the restaurants of one national chain. Thus, hemorrhagic colitis due to E, coli 0157:H7 is commonly referred to as hamburger disease.

What are the complications of infection with E. coli 0157:H7?

Hemorrhagic diarrhea (hemorrhagic enterocolitis)
The incubation period between exposure to EHEC bacteria and the onset of symptoms is usually three to four days. Symptoms EHEC infection include severe abdominal pain and abdominal tenderness which often is associated with bloody diarrhea. Curiously, there often is little or no fever. The diarrhea typically lasts for six to eight days. 

Hemolytic-uremic syndrome
(HUS) is the most worrisome complication of EHEC infection because it is a serious and potentially fatal illness. "Hemolytic" refers to the breakup of red blood cells which leads to anemia. There also is destruction of platelets which leads to low blood levels of platelets (thrombocytopenia) which, in turn, promotes abnormal bleeding. "Uremic" refers to failure of the kidneys. In addition, problems in the brain with seizures and coma may occur. Hemolytic-uremic syndrome most commonly affects children under the ages of 10 years and is the most common cause of acute renal failure in infants and young children. It occurs in 6%-9% of hemorrhagic colitis caused by E coli 0157:H7 and usually occurs approximately 7 to 10 days after the onset of diarrhea.  

Thrombotic thrombocytopenic purpura
Persons infected with E. coli 0157:H7, particularly the elderly, can develop a syndrome similar to hemolytic-uremic syndrome called thrombotic thrombocytopenic purpura (TTP) with clotting of blood within small blood vessels, anemia due to fragmentation of red blood cells, and shortage of platelets (thrombocytopenia) that results in easy bruising, neurologic abnormalities, impaired kidney function, and fever. Thrombotic thrombocytopenic purpura, once almost always fatal, is still a serious consequence of E. coli 0157:H7.

How do people get E. coli 0157:H7?

Most commonly, E. coli 0157:H7 comes from eating raw or undercooked ground beef (hamburger) or from drinking raw milk. Less commonly, E coli O157:H7 can be transmitted from one person to another.

What are the symptoms of E. Coli, and how is it diagnosed?

In patients suspected of having E. coli 0157:H7 infection (for example, patients with bloody diarrhea, severe abdominal pain and tenderness with no fever), a stool specimen is tested for the presence of E. coli O157:H7. Some hospitals test for E. coli 0157:H7 in all stool samples submitted to their laboratories while others only test for E. coli 0157:H7 in samples from patients with bloody diarrhea. Still others only test for E. coli 0157:H7 upon request by the doctors. There are two methods of testing for E. coli 0157:H7 in stool samples:

1) growing the bacteria in culture dishes

2) testing for the shiga toxin produced by the bacteria. Even though toxin detection methods are becoming more common, it is important to confirm the presence of E. coli 0157:H7 in cultures of stool containing toxin.Blood tests such as complete blood count (CBC), and blood levels of electrolytes, blood urea nitrogen (BUN), and creatinine (blood tests that measure function of the kidney) are performed periodically to look for the development of hemolytic-uremic syndrome.

What is the treatment for E. coli 0157:H7?

For the acute diarrheal illness, antibiotics have not proven useful. In fact, some studies have shown that antibiotic use may increase the chances of developing hemolytic-uremic syndrome. Treatment includes the replacement of fluids and electrolytes to prevent dehydration. Infection with E. coli 0157:H7 should be treated by a physician. Hemolytic-uremic syndrome and thrombotic thrombocytopenic purpura require complex supportive care in the hospital. Patients with kidney failure may need dialysis.
 
How can you prevent infection with E. coli 0157:H7?

The following precautions are recommended.Handle raw meat correctly

• Put raw ground beef (hamburger) in the refrigerator or freezer as soon as possible until ready to use.
• Thaw frozen meat by putting it in the refrigerator or in the microwave.
• NEVER thaw meat at room temperature.
• Wash everything touched by raw meat with warm soapy water.
• Wash work surfaces, dishes, utensils, and your hands.

• Cook burgers thoroughly. The inside of the patty should not be pink. If it is, cook the burger longer. When you cut it, the meat should not be pink and the juice should be clear.
• In a restaurant, order burgers cooked "medium well" or "well done." If you see pink or if the juice is not clear, send the burger back to the kitchen for additional cooking.

• Avoid raw milk and raw milk products. Raw milk is not healthier.
• Consume only pasteurized milk and milk products.

• Drink water from a well only if you know it's free from contamination.
• Do not drink untreated water from streams or lakes.

• Wash your hands with soap and water before and after handling food. It cuts the risk of spreading E. coli (and other germs).
• Be sure children wash their hands carefully and often