Escherichia coli

Escherichia coli overview and Definition

Escherichia coli (E. coli) bacteria normally live in the intestines of healthy people and animals. Most types of E. coli are harmless or cause relatively brief diarrhea. But a few strains, such as E. coli O157:H7, can cause severe stomach cramps, bloody diarrhea and vomiting. It also plays a vital role in urinary tract infections.

The person might be exposed to E. coli from contaminated water or food — especially raw vegetables and undercooked ground beef. Healthy adults usually recover from infection with E. coli O157:H7 within a week. Young children and older adults have a greater risk of developing a life-threatening form of kidney failure


After ingestion of E. coli O157: H7, the bacteria bind to the intestinal mucosa and begin releasing Shiga toxin. The toxin, in turn, disrupts protein synthesis in the epithelial cells lining intestinal mucosa, leading to cell death, sloughing of the mucosa, and eventual bloody diarrhea.  Following exposure to the Shiga toxin, diarrhea, often the hemorrhagic variety, develops three days after exposure to the contaminated food specimen. After three days of diarrheal symptoms, diarrhea will become bloody in approximately 90% of affected patients. 

Clinical signs & symptoms

Symptoms of infection with E. coli 0157. It typically appears 2-4 days after being exposed to the bacteria. However, symptoms may appear as early as 24 hours or as late as 1 week later.

These can include:

  • abdominal pain or severe abdominal cramping, often starting suddenly
  • watery diarrhea, beginning a few hours after the pain begins
  • bright red bloody stools around a day later, resulting from the toxin’s damage to the intestines
  • nausea and, in some cases, vomiting
  • in some cases, fever, usually below 101 degrees Fahrenheit
  • fatigue resulting from dehydration and the loss of fluids and electrolytes.

Differential Diagnosis

Stool and urine culture:

Isolation of the organisms and susceptibility profile and laboratory investigations are made.

Molecular and Rapid tests:

This includes immunochromatographic lateral flow devices such as dipsticks which can detect the presence of the O157 antigen in stool samples.



The prognosis is good and the infection caused by the bacterium can be subsided within 2-3 weeks.


When thawing meats:

  • Don’t defrost frozen meat unwrapped on the counter.
  • Keep frozen meat in a separate plastic bag (for example, a plastic grocery bag) when thawing.

When prepping foods:

  • Don’t rinse meat before cooking. It’s not necessary. Washing the meat could spread bacterial to nearby surfaces, utensils and other food.
  • Use a plastic or ceramic cutting board to cut raw meat. These materials can be cleaned more easily and thoroughly than wooden cutting boards.
  • Don’t “cross-contaminate” a prepping surface. If you had raw meat or chicken on a prepping surface, such as a cutting board, wash it thoroughly with soap and hot water before putting another type of food (such as a raw vegetable) on it. Better yet, use different cutting boards for the foods you are preparing.
  • Rinse all raw fruits and vegetables under cold running water before eating them. It’s ok to scrub firm produce but don’t use detergent or soap.

When cooking and serving meats:

  • Cook all meat well (undercooked meat is another source of E. coli contamination). Cooking foods well kills bacteria.
  • Use a food thermometer when cooking meat, and cook all meat and other foods to the safe temperatures recommended by the United States Department of Agriculture (see references for link).
  • Don’t put a cooked hamburger on a plate that had raw ground beef or any other raw meat on it.
  • Refrigerate leftovers right away.