E. Coli Infections

Escherichia coli are bacteria of which the virulent strains can cause significant gastrointestinal morbidity and mortality. E. coli O157:H7 is the strain most well known to the general public for causing epidemics after ingestion of contaminated water and foods, including undercooked hamburgers, lettuce, and spinach. The Centers for Disease Control and Prevention estimates that over 73,000 cases of infection and 61 deaths occur in the United States annually because of E. coli O157:H7.

First isolated in 1982, E. coli O157:H7's virulence stems from its ability to produce several toxins. These toxins have the ability to invade the gastrointestinal mucosal surfaces, causing a range of symptoms including asymptomatic infections, severe abdominal cramps with or without fever, watery diarrhea, or grossly bloody diarrhea. More severe diseases may also occur. Hemolytic uremic syndrome causes a blood disorder, acute renal failure, and neurological symptoms, while thrombocytopenic purpura can cause low platelets. Among reported U.S. outbreaks, 23 percent of patients were hospitalized, 6 percent had hemolytic uremic syndrome or thrombocytopenic purpura, and approximately 1percent died from E. coli infections.

E. coli is ubiquitous around the world. The incidence and prevalence of E. coli infections remain underreported because many infected persons do not report to their physician when they are infected, the physician does not send the correct laboratory test for definitive diagnosis, or the physician does not report the infection to the proper authorities. Seasonally, E. coli infections occur more frequently in the summer, which may be due to the higher consumption of ground meats during outdoor barbeques.

Transmission of E. coli to humans occurs primarily through the contamination of the food and water supply. E. coli O157:H7 can be found in the intestines of cattle, deer, goats, and sheep. The meat may be contaminated through slaughter or through the process of grinding the meat. Additionally, E. coli can infect raw milk if the bacteria have colonized cows’ udders.

E. coli is also found in sprouts, salami, and unpasteurized milk and juice. Swimming or drinking sewage-contaminated water can also be a means of transmission. Handling infected stools or inadequate hand washing can also transmit E. coli rapidly, especially among toddlers and young children.

Once E. coli infection is suspected, the diagnosis can be confirmed by growing colonies of the bacteria and then assaying the colonies for the O157 antigen, the protein that causes the infection. Although it is recommended that all physicians screen for E. coli, only one-quarter of laboratories actually screen all stool specimens. Because the antigen declines steeply after six days of illness, it is imperative to culture stools early. Currently, rapid detection tests are being developed.

No specific treatment exists for E. coli infection. Most infected people recover from this self-limiting [Page 583]illness within five to 10 days. Studies have not found antibiotics to be effective, and in some cases, antibiotics have worsened the illness. Antimotility agents (i.e. Immodium) should not be used in infected patients. One study found that patients who used antimotility agents were at increased risk to develop hemolytic uremic syndrome. In terms of prevention, a safe food supply and better hygiene practices can help curb the incidence of E. coli infections. Physicians should counsel patients on proper handling of meat, including correct cooking temperatures, hand washing, using only treated water for cooking and drinking, and drinking only pasteurized liquids.

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