Shiga-Toxin Escherichia coli: What You Should Know About this Group of Foodborne Pathogens

HYG-5561
Family and Consumer Sciences
Date: 
11/30/2011
Written by Lydia Medeiros, Jeffery LeJeune, and Michele Williams.

There are a variety of Escherichia coli bacteria present in nature. They are usually found in the intestines of healthy humans and healthy animals. Even though these bacteria offer beneficial properties, there are some strains that are pathogenic, or have the ability to cause serious disease. The most severe strains produce the Shiga toxin; thus, a larger group of pathogenic E. coli is called Shiga-Toxin Escherichia coli, or STEC.

Symptoms of illness

The foodborne illness caused by STEC can be mild causing only watery diarrhea and abdominal cramps. Occasionally there will be a low-grade fever. Mild cases usually last around eight days and do not require medical treatment other than fluids to treat dehydration. Antibiotics are not recommended for STEC infections as there is no evidence that the usage of antibiotics is helpful and they may even increase the risk of hemolytic uremic syndrome (HUS), a potentially life-threatening complication of STEC infections. Antidiarrheal agents may also increase the risk of developing HUS.

Some more severe cases are characterized by bloody diarrhea. Medical treatment is necessary if this symptom develops. On rare occasions, some cases are so severe that the person develops HUS, which can lead to permanent kidney failure. Children and elderly are the age groups most susceptible to HUS. If an elderly person develops HUS, they could also develop thrombotic thrombocytopenic purpura (TTP), a blood disorder that causes blood clots to form in small blood vessels around the body, and leads to a low platelet count. Bleeding under the skin can occur, which causes purplish spots called purpura. Fifty percent of TTP cases in the elderly are fatal.

Public health consequences

The exact number of STEC cases that occur each year is hard to determine because many people attribute their illness to a virus or flu. The local Health Department and Centers for Disease Control and Prevention (CDC) cannot record the number of cases accurately unless the ill person seeks medical care, which is unusual in mild cases. The CDC has calculated an estimate of the number of cases of STEC illness based on corrections for under reporting, misdiagnosis, and the number of cases that are not caused by contaminated food.

The CDC estimates that there are more than 175,000 cases of STEC each year in this country, and that 60–80% of the cases are caused by eating contaminated food. Over 2,000 cases will be severe enough to require hospitalization; 20 deaths are possible each year. Most cases occur in children younger than 9 years old (2–5 cases/100,000 population), but any age group is susceptible. Young children are vulnerable due to their immature immune systems.

Foods implicated

The most frequently known outbreaks of STEC bacteria are associated with fecal contaminated meats in slaughterhouses. However, it is also associated with contaminated water, raw or unpasteurized milk, unpasteurized juice or apple cider, raw vegetables, and undercooked beef, poultry, venison, and lamb.

Pathogen control methods

1. Use a thermometer to make sure that meat and poultry (including ground types) are cooked to safe temperatures.

  1. The only way to be sure meat and poultry are done is to check with a food thermometer.
  2. Follow the safe cooking advice on packages.
  3. The thermometer should go into the thickest part of the chicken or turkey.
  4. Cook poultry until the food thermometer says at least 160 degrees F (71 degrees C).

2. Drink only pasteurized milk.

  1. Children are very susceptible to STEC infections and should not drink raw milk.
  2. Only buy cheeses made from pasteurized milk, or that have been aged at a minimum of 60 days.

3. Drink only pasteurized fruit juices.

  1. In stores, fruit juice that has not been pasteurized must display a warning label.
  2. Keep freshly squeezed juice cold. Refrigerate any leftovers.
  3. If the juice has not been pasteurized, don't drink it, or heat it until it boils. Cool the juice before drinking.

4. Knives, cutting boards, and food preparation surfaces should be washed with hot water and soap after contact with raw poultry, meat, and seafood.

  1. Clean sinks and counters with paper towels or clean cloths and hot soapy water before and after cooking food.
  2. Keep foods that are ready to eat away from raw meat or poultry.
  3. Wash knives, cutting boards, and counters with hot water and soap after you work with raw meat, chicken, or turkey.
  4. Scrub your cutting board with dish soap. If your cutting board is not made of wood, you can put it into the dishwasher.
  5. Put thawing meat in a dish in the refrigerator to keep juices from leaking onto the food below.

5. Wash hands with warm, soapy water before and after handling raw foods.

  1. First, wet your hands.
  2. Add soap to your hands.
  3. Rub both sides for at least 20 seconds.
  4. Rinse thoroughly.
  5. Air dry, or dry with a clean towel or paper towel.
  6. Always wash your hands after using the toilet, after changing a baby's diaper, after touching pets or other animals, and after sneezing or coughing.

6. Wash fruits and vegetables before eating them.

  1. Do not eat raw alfalfa and other sprouts.
  2. Use water from a safe water supply for drinking and washing fresh produce.
  3. Remove outer wilted and damaged areas before washing.
  4. Only wash and prepare the amount you will use in one meal.
  5. Refrigerate remaining vegetables without washing or dry with a paper towel or in a salad spinner.

References

Centers for Disease Control and Prevention. Vital signs: Incidence and trends of infection with pathogens transmitted commonly through food—foodborne diseases active surveillance network, 10 U.S. sites, 1996–2010. Morbidity and Mortality Weekly 2011; 60 (22): 749–755.

Hillers, V.N., Medeiros, L.C., Kendall, P., Chen, G., & DiMascola, S. Consumer food handling behaviors associated with prevention of 13 foodborne illnesses. Journal of Food Protection 2003; 66: 1893–1899.

Scallan, E., Hoekstra, R.M., Angulo, F.J., Tauxe, R.V., Widdowson, M.A., Roy, S.L., Jones, J.L., & Griffin, P.M. Foodborne illness acquired in the United States—major pathogens. Emerging Infectious Diseases 2011; 17: 7–15.

U.S. Food and Drug Administration. Escherichia coli O157:H7. The Bad Bug Book. fda.gov/Food/FoodSafety/FoodborneIllness/FoodborneIllnessFoodbornePathogensNaturalToxins/BadBugBook/ucm071284.htm. Accessed: February 11, 2010.

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