Bloody Diarrhea Caused by E. coli O157:H7

E coli in hamburger. Vito Aluia/photolibrary/Getty Images

Although not identified as a cause of hemorrhagic colitis (bloody diarrhea) until 1982, E. coli O157:H7 is now recognized as a common cause of this condition. Outbreaks of colitis caused by this bacteria have been associated with tainted hamburger, apple juice, and unpasteurized dairy products. Although most infections are not serious and resolve on their own, potentially deadly complications can occur following infections by E. coli O157:H7.

Species Name: Enterohemorrhagic Escherichia coli, or “EHEC”

Type of Microbe: Gram-negative bacteria

How it spreads: Usually foodborne.

Foods associated with E. coli have included raw or undercooked meats (e.g., ground beef), deli meats, unpasteurized fruit juices and dairy products, and produce. Other sources of infection have included petting zoos, lake water, and contaminated hands.

Who’s at risk? All people are susceptible to the disease, but the very young and very old are at greater risk for more serious disease.

Symptoms: Symptoms may vary, but usually include diarrhea (usually bloody), vomiting, and severe stomach cramps. Typically, fever is absent or very mild. For most people, the infection resolves by around 8 days.

How it causes disease: E. coli attaches to intestinal cells and produces a toxin (Shiga toxin) that causes inflammation and secretion of intestinal fluids. The toxin also damages the tissue lining of the large intestine and kidneys.

Complications: About 5-10% of individuals with E. coli O157:H7 infections develop a potentially fatal complication called hemolytic-uremic syndrome, or HUS, which is characterized by kidney or renal failure and hemolytic anemia (loss of red blood cells). This condition usually occurs in children and can be quite serious, leading to permanent kidney damage or death.

Diagnosis: Lab testing of stool samples is performed with bacterial cultures.

Prognosis: Most infections resolve on their own within 5 to 7 days without treatment, but some infections can be severe or life-threatening.

Treatment: Treatment consists of supportive care, in particular, avoiding dehydration by administering fluids. Antibiotics and anti-diarrheal medicines (such as Imodium) are specifically not recommended for treating E. coli O157:H7 infections. The use of these medications has been associated with more severe illness - apparently, they can lengthen the duration of diarrhea, potentiate the effects of Shiga toxin, and increase the risk of hemolytic-uremic syndrome.

Prevention: Use good hygiene, frequent hand washing, and kitchen safety practices.

Sources:

Escherichia coli. CDC Division of Foodborne, Bacterial and Mycotic Diseases.

Escherichia coli O157:H7. US FDA Bad Bug Book. Foodborne Pathogenic Microorganisms and Natural Toxins Handbook.

Tarr PI, Gordon CA, Chandler WL. Shiga-toxin-producing Escherichia coli and haemolytic uraemic syndrome. Lancet 2005; 365:1073.

Edited by Richard N. Fogoros, MD

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