Escherichia Coli

Escherichia coli, more often known as E. coli, is a bacterium commonly found in the digestive system of humans and animals. There are hundreds of different strains of E. coli. Although they are generally harmless, there are some that cause severe illness. The most widely known harmful strain is E. coli O157:H7.

E. coli O157:H7 is a shiga-toxin-producing gramnegative bacterium that causes foodborne illness. It is usually found in the intestine of cattle and produces large quantities of the shiga-like toxin, a verotoxin, which causes severe damage to the lining of the intestine in infected individuals. Ground beef is the most common source of contamination, typically caused by the undercooking of beef that became infected during slaughter. Other sources of contamination include unpasteurized milk and juice, lettuce, sprouts, and water.

E. coli O157:H7 was first identified as a source of illness in 1982 in an outbreak of severe diarrhea among 47 people from Michigan and Oregon caused by hamburgers from a fast-food restaurant contaminated with the bacteria. It became a reportable disease in the United States in 1987. Most cases have been reported in the United States, Canada, and the [Page 337]United Kingdom. However, the largest recorded outbreak of E. coli O157:H7 occurred in Japan in 1996. It affected more than 6,300 children and caused two deaths. This outbreak was associated with consumption of radish sprouts served in elementary school lunches in Japan.

Infection is diagnosed by detecting E. coli O157:H7 in a stool sample. Infected individuals typically experience symptoms that include severe abdominal pain and bloody diarrhea. These symptoms can last for approximately 5 to 10 days. In severe cases, kidney failure may result, called hemolytic uremic syndrome. While rare, this most commonly occurs in the elderly and young children, and treatment typically includes blood transfusions and kidney dialysis. Although it can affect individuals of all ages, young children are the most at risk of developing serious complications.

Although transmission is primarily foodborne, infection can be secondarily passed from person to person and has been documented in some day care and nursing home outbreaks. Secondary transmissions are typically the result of improper hand washing and poor hygiene, resulting in the transmission of bacteria from fecal contamination. E. coli O157:H7 causes approximately 73,000 illnesses in the United States each year and 60 deaths. However, these are likely underestimates of the true prevalence given the numbers of infected individuals who do not seek medical treatment and, therefore, are not captured in the public health surveillance system. Preventive measures such as proper hand washing and thoroughly cooking meat are suggested as ways to minimize transmission of E. coli O157:H7.