Escherichia coli (E. coli) is a bacterium commonly found in the gut of warm-blooded organisms. Most E. coli strains pose no harm to humans. However, there are six groups of E. coli known for their ability to cause human illness.
E. coli also prevent harmful bacteria from establishing themselves in the intestine.
The strain most often associated with disease in humans is called O157:H7. This strain of E. coli can cause an intestinal infection and become life-threatening.
A healthy adult will usually make a full recovery from E. coli O157:H7 infection within 5-7 days. However, young children, pregnant women, elderly individuals, and patients with weakened immune systems are more susceptible to foodborne illnesses.
They can also develop potentially fatal HUS (hemolytic uremic syndrome), a complication of E. coli infection that causes a type of kidney failure.
Fast facts on E. coli
Here are some key points about E. coli. More detail and supporting information is in the main article.
- Most strains of E. coli are harmless to humans
- Symptoms of E. coli infection can include nausea, vomiting, and fever
- Diagnosis can be reached by testing a stool sample
- In susceptible individuals, E. coli infection can lead to kidney failure
- Keeping one's hands clean at all times helps prevent its spread
Causes of E. coli infection
Although most strains of E. coli are harmless, some produce a toxin that makes humans sick.
There are several types of toxins; the group that includes 0157:H7 produces a potent toxin called Shiga toxin that is harmful to the lining of the small intestine.
Humans can become infected by:
- Ingesting contaminated water - even though tap water contains chlorine and has undergone ozone or ultraviolet treatment, some E. coli outbreaks have been caused by contaminated municipal water supplies. Private wells can be a source of infection, as can some lakes and swimming pools.
- Ingesting contaminated food - examples include undercooked ground beef, unpasteurized milk, or raw vegetables. Infected people who work in restaurants and do not wash their hands properly after going to the toilet can spread the infection to customers and other members of staff.
- Person-to-person contact - good hand hygiene is important in stopping the spread of infection.
- Contact with animals - this can occur in farms, petting zoos, and fairs.
High fiber diets
Researchers from the Uniformed Services University of the Health Sciences found that people who consumed high fiber diets had a higher risk of harboring E. coli bacteria, suffering the consequences of O157:H7 infection, and were prone to developing more severe cases of disease.
The authors concluded that "dietary choice affects Shiga-toxin-producing Escherichia coli (STEC) O157:H7 colonization and disease."
Symptoms of E. coli infection
The length of time between E.coli infection and the start of symptoms can vary.
The patient will typically experience symptoms within 3-4 days after being exposed to the bacteria; however, in some cases, symptoms may appear within 24 hours, or 1 week later.
Symptoms can include:
- Abdominal pain - typically, the first symptom is severe abdominal cramping that often comes on suddenly.
- Diarrhea - a few hours after the sudden abdominal pain, the patient typically has watery diarrhea. A day later there may be bright red bloody stools, caused by the toxin's damage to the intestines.
- Vomiting - however, many patients who become ill do not vomit.
- Fever - low grade, usually less than 101 degrees Fahrenheit; but, many infected people do not have a fever
- Fatigue - diarrhea causes loss of fluids and electrolytes (dehydration), making the patient feel sick and tired.
A considerable number of infected people have no noticeable symptoms. However, they are capable of unwittingly spreading the infection to others.
E. coli infection risk factors
The following risk factors are linked to a higher chance of E. coli infection:
- Certain foods - the foods most commonly contaminated by E. coli are unpasteurized milk, juice, cider, and cheese, undercooked ground beef, and alfalfa sprouts.
- Immunocompromised patients - complications are more common in those with weakened immune systems, such as patients with AIDS, those taking immunosuppressive medications, and people receiving chemotherapy.
- Reduced stomach acid - patients who have decreased stomach acid, either due to stomach surgery or medicines that lower stomach acid, have a higher risk of infections.
- The person's age - very young children and seniors have a higher risk of developing serious illness and complications.
E. coli infection complications
The vast majority of infected individuals make a full recovery within a week. However, those who are susceptible may develop hemolytic uremic syndrome (HUS). Overall, this complication affects about 10 percent of people who develop an E. coli infection.
HUS is characterized by hemolysis (breakup of red blood cells) causing anemia, a low platelet count, and kidney failure. Platelets, the blood cells that are responsible for blood clotting, clump together within the small blood vessels of the kidneys, resulting in reduced blood flow (ischemia) and eventually lead to kidney failure. Decreased platelets increase the risk of bleeding problems.
The patient can also develop central nervous system (brain and spinal cord) problems from these blood clots, causing seizures, paralysis, brain swelling, and coma. Acute kidney failure among infants and young children is usually caused by HUS.
The majority of people who develop HUS are young children and elderly individuals.
Diagnosis of E. coli infection
The doctor identifies the signs, asks the patients about symptoms, and sends a stool sample to a lab for analysis.
Treatments for E. coli infection
There is no cure for E. coli O157:H7, it has to run its course. Most doctors advise patients to get plenty of rest and drink lots of water to prevent dehydration.
The patient should avoid taking OTC medications for diarrhea, as this can slow down the digestive system, undermining the body's ability to eliminate the toxins efficiently.
Prevention of E. coli infection
- Cook meat well - especially ground meat.
- Drinks - pasteurized milk, apple juice, and cider are safer than unpasteurized.
- Wash vegetables - especially leafy green ones. Washing thoroughly might not protect you completely, but it helps.
- Wash cutlery and crockery - make sure knives, forks, plates, and serving dishes are thoroughly washed with warm, soapy water.
- Store foods separately - use separate cutting boards, do not store raw ground beef right next to other foods.
- Hand hygiene - wash your hands thoroughly with warm water and soap after going to the toilet, after changing diapers, before and after preparing foods, and after touching animals. Wash your hands regularly.