Escherichia coli 0157:H7, or E. coli

Filed Under: Cows, Diseases

Escherichia coli, also known as E. coli, is a normal bacterial inhabitant of the intestinal tract of both humans and animals. E. coli is a gram-negative bacterial rod. Most strains of E. coli are not pathogenic, but some strains are known to cause disease. Most infections by pathogenic E. coli will cause disease in the intestinal tract resulting in diarrhea and inflammation of the intestines. There are still other strains known to be more virulent (capable of producing a more severe disease syndrome) and will produce an enterohemorrhagic toxin which causes bloody diarrhea. The most virulent strain is Escherichia coli 0157:H7. The potent cytotoxin produced by E. coli 0157:H7 is also known as the Shiga toxin (Stx). The natural hosts of Shiga toxin-producing E. coli are farm and wildlife ruminants such as cows, sheep, goats, and deer.

Animals infected with enteric (intestinal) pathogens may have no clinical signs of illness and pathogens may be shed intermittently. Environmental contamination can be widespread and persistent.

The 0157:H7 strain of E. coli became infamous in the mid-nineties when an outbreak of food-borne illness occurred from a “Jack in the Box” restaurant in Oregon. This was the first reported case where a strain of bacteria was implemented in being an adulterant in raw meat. Hamburgers from the restaurant were not fully cooked, resulting in food-borne infections with their patrons.

In 2006, deaths from E. coli 0157:H7 resulted from bagged spinach believed to have come from greens that were contaminated by cattle waste. It is still unknown how the bacteria were spread throughout the spinach fields. The University of California-Davis School of Veterinary Medicine (UC-Davis) is investigating possible sources of contamination in the Salinas Valley.

The most prominent symptom of infection with E. coli 0157:H7-producing Shiga toxins are a hemorrhagic colitis (bloody diarrhea). Additional symptoms include painful abdominal cramps and dehydration. In some patients, the hemorrhagic colitis can progress into one of two additional syndromes: the hemolytic uremic syndrome (HUS) or thrombotic thrombocytopenic purpura (TTP). The HUS usually appears about seven days after the onset of diarrhea and affects children under ten years of age most severely. The HUS results in the breakdown of red blood cells and platelets, as well as renal failure. According to the CDC, the use of antibiotics may even aggravate the condition. In elderly individuals, the TTP syndrome is more commonly seen. TTP is characterized by a destruction of platelets resulting in hemorrage. Although the United States has the safest food supplies in the world, the Center for Disease Control (CDC) estimates that E. coli O157:H7 causes 73,500 illnesses, 2,000 hospital stays, and 60 deaths in the United States every year.

The E. coli 0157:H7 infection can be transmitted by contaminated food, water, and contact with fecal material from infected persons or animals. Many of the infections are also associated with consumption of undercooked meat, as well as contact with farm animals or animals in a petting zoo situation.

In an effort to decrease the incidence of infection with E. coli 0157:H7, researchers at the University of Nebraska are presently working on a cattle vaccine. Early trials have shown the bacterin to decrease E. coli numbers by 70% in the manure of infected animals.

Tufts University is presently conducting research targeting the toxin of E. coli. They have produced antibodies to the 0157:H7 strain that were administered to pigs infected with E. coli after the onset of diarrhea. The antibody treatment prevented systemic kidney and brain damage. According to school officials, enough antibodies have been produced that they will start clinical trials in humans.

For now, safe food handling and preparation are the number one way consumers can protect themselves and their families from E.coli 0157:H7. Always cook ground beef products to an internal temperature to 160°F. In the kitchen, it is imperative to keep raw and cooked products separated and prevent contamination between the two. Cooked vegetables are safer to consume than are raw ones. Raw fruits and vegetables should be washed thoroughly before consuming.

To prevent zoonotic infections, people should not eat, drink, or have hand-to-face contact in animal contact areas such as petting zoos. Once a visit to a petting zoo has been completed hands should be sanitized.


“Petting Zoos”. Antech Diagnostics News. December 2007.

McMillian, Marcy, John Dunn, James Keen. Et al. “Risk Behaviors for Disease Transmission among Petting Zoo Attendees.” JAVMA, Vol. 231, No. 7, October 1, 2007. Pp. 1036-1038.

“Veterinary institutions Study E. coli O157:H7.” DVM News. November 2006. P. 13.

“Animal Health Newsletter”, Alabama Department of Agriculture and Industries. USDA, APHIS, Veterinary Services. Vol 1, Issue 3 September/October 2007. P. 1.

Topics: e. coli

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