Escherichia coli (E. coli) are a group of gram-negative bacteria that normally reside in the intestine of healthy people, but some strains can cause infection in the digestive tract, urinary tract, or many other parts of the body.
Urinary tract infections are the most common infection caused by E. coli, and people may also develop intestinal infections by eating contaminated food (such as undercooked ground beef), touching infected animals, or swallowing contaminated water.
Intestinal infections can cause diarrhea, sometimes severe or bloody, and abdominal pain.
Antibiotics can effectively treat E. coli infections outside the digestive tract and most intestinal infections but are not used to treat intestinal infections caused by one of strains of these bacteria.
(See also Overview of Bacteria.)
Some strains of E. coli normally inhabit the digestive tract of healthy people. However, some strains of E. coli have acquired genes that enable them to cause infection.
The most common infection caused by E. coli is
In women, E. coli is the most common cause of
Other infections that can result from E. coli include the following:
Digestive tract (causing gastroenteritis)
Infection of the prostate gland (prostatitis)
Gallbladder infection
Infections that develop after appendicitis and diverticulitis
Wound infections (including wounds made during surgery)
Infections in pressure sores
Many E. coli infections affecting areas outside the digestive tract develop in people who are debilitated, who are staying in a health care facility, or who have taken antibiotics.
E. coli can cause infections outside the intestine if the intestine is torn or damaged—for example, by an injury or a disorder, such as inflammatory bowel disease. Then, the bacteria may leave the intestine and spread to nearby structures that have no defenses against them or they may enter the bloodstream.
One strain produces a toxin that causes brief watery diarrhea. This disorder (called traveler’s diarrhea) usually occurs in travelers who consume contaminated food or water in areas where water is not adequately purified.
E. coli O157:H7 infection
Certain strains of E. coli produce toxins that damage the colon and cause severe inflammation (colitis—see also E. coli gastroenteritis). In North America, E. coli O157:H7 is the most common of these strains, but there are over 100 others. These strains are sometimes collectively referred to as enterohemorrhagic E. coli (entero means intestinal, and hemorrhagic means bleeding).
People are usually infected with these strains by doing the following:
Eating contaminated ground beef that is not cooked thoroughly (one of the most common sources) or drinking unpasteurized milk
Going to a petting zoo and touching animals that carry the bacteria in their digestive tract
Eating ready-to-eat food (such as produce at salad bars) that was washed with contaminated water or contaminated by cattle manure
Swallowing inadequately chlorinated water that has been contaminated by the stool of infected people in swimming or wading pools
Inadequate hygiene, particularly common among young children in diapers, can easily spread the bacteria from person to person.
E. coli O157:H7 infection can occur in people of all ages, although severe infection is most common among children and older adults.
Symptoms of E. coli Infections
E. coli symptoms depend on the part of the body affected and on the strain of E. coli causing the infection.
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Traveler's diarrhea
People with traveler’s diarrhea have abdominal cramping and watery diarrhea and sometimes nausea and vomiting. Symptoms are usually mild and resolve in 3 to 5 days.
E. coli O157:H7
Infections due to E. coli O157:H7 and other enterohemorrhagic E. coli typically begin with severe abdominal cramps and watery diarrhea, which may become bloody within 24 hours. (This disease is sometimes called hemorrhagic colitis—see also E. coli gastroenteritis.) People usually have severe abdominal pain and diarrhea many times a day. They also often feel an urge to defecate but may not be able to. Most people do not have a fever.
Because the infection is easily spread, people must often be hospitalized and isolated.
The diarrhea may resolve on its own in 1 to 8 days if no problems develop. However, E. coli O157:H7 infection is often very severe and may cause serious problems (such as hemolytic-uremic syndrome) as the diarrhea lessens. Also, the bacteria may continue to reside in a person's intestinal tract after symptoms resolve and continue to cause repeated infection in the person or transmission of the bacteria to other people.
Hemolytic-uremic syndrome is a complication that develops in up to 22% of people (mainly children under 5 years and adults over 60 years) about 1 week after symptoms begin. In this syndrome, red blood cells are destroyed (called hemolysis), and kidney failure occurs, causing toxic substances to build up in the blood (called uremia). This complication is a common cause of chronic kidney disease in children.
E. coli O157:H7 infection may result in death, especially in older adults, whether hemolytic-uremic syndrome develops or not.
Diagnosis of E. coli Infections
Culture of samples of urine, stool, or other infected material
Samples of blood, stool, urine, or other infected material are taken and sent to a laboratory to grow (culture) the bacteria. Identifying the bacteria in the sample confirms the diagnosis.
If E. coli O157:H7 is suspected, doctors culture and test stool for Shiga toxins, which are produced by these bacteria. This test provides results quickly.
If the bacteria are identified, they may be tested to see which antibiotics are effective (a process called susceptibility testing).
If E. coli O157:H7 is detected, blood tests must be done frequently to check for hemolytic-uremic syndrome.
Treatment of E. coli Infections
For many infections, antibiotics
For diarrhea due to E. coli O157:H7, fluids
Treatment of E. coli infection varies depending on
Where the infection is
How severe it is
Which type of E. coli is causing it
For example, if infections have caused an abscess, surgery may be done to drain the pus.
Traveler's diarrhea
People with traveler’s diarrhea should drink plenty of fluids.
If diarrhea is accompanied by a fever or is bloody, travelers should see a doctor.
Diarrhea due to E. coli O157:H7
Many people with diarrhea due to E. coli O157:H7 need to be given fluids containing salts intravenously.
This infection is not treated with loperamide or antibiotics. Antibiotics may make diarrhea worse and increase the risk of hemolytic-uremic syndrome, and loperamide may cause other complications.
If hemolytic-uremic syndrome develops, people are admitted to an intensive care unit and may require hemodialysis.
Other E. coli infections
Many other E. coli infections, usually bladder or other urinary tract infections
For more serious infections, antibiotics that are effective against many different bacteria (broad-spectrum antibiotics) may be used.
Prevention of E. coli Infections
Prevention of urinary tract infections caused by E. coli involves drinking enough fluids and avoiding contamination of the urethra (the opening where urine comes out) with stool. Females, for example, should wipe from front to back after urinating or having a bowel movement.
Prevention of E. coli O157:H7 infection involves
Avoiding unpasteurized milk and other dairy products made from unpasteurized milk
Thoroughly cooking beef
Thoroughly washing the hands with soap and running water after using the toilet, changing diapers, and having contact with animals or their environment and before and after preparing or eating food
Not swallowing water when swimming or when playing in lakes, ponds, streams, swimming pools, or backyard "kiddie" pools
In the United States, improved meat processing procedures have helped reduce the rate of meat contamination.
To prevent spread of infection in day care centers, staff members may separate children who are not infected from children who are known to be infected. Or they may ask for proof that the infection is gone (negative results on two stool cultures) before they allow infected children to attend.
More Information
The following English-language resource may be useful. Please note that THE MANUAL is not responsible for the content of this resource.
Centers for Disease Control and Prevention (CDC): E. coli: A resource providing information about E. coli, including outbreaks and prevention
