E. coli normally inhabit the gastrointestinal tract; however, some strains have acquired genes that enable them to cause intestinal infection. When ingested, the following strains can cause diarrhea:
Enterohemorrhagic E. coli is the most clinically significant subtype in the US. It produces Shiga toxin, which causes bloody diarrhea (hemorrhagic colitis). Thus, this subtype is sometimes termed Shiga toxin–producing E. coli (STEC). E. coli O157:H7 Infection by Escherichia coli O157:H7 and Other Enterohemorrhagic E. coli (EHEC) The gram-negative bacteria Escherichia coli O157:H7 and other enterohemorrhagic E. coli (EHEC) typically cause acute bloody diarrhea, which may lead to hemolytic-uremic syndrome... read more is the most common strain of this subtype in the US. Undercooked ground beef, unpasteurized milk and juice, and contaminated water are possible sources. Person-to-person transmission is common in the day care setting. Outbreaks associated with exposure to water in recreational settings (eg, pools, lakes, water parks) have also been reported. Hemolytic-uremic syndrome Hemolytic-Uremic Syndrome (HUS) Hemolytic-uremic syndrome (HUS) is an acute, fulminant disorder characterized by thrombocytopenia, microangiopathic hemolytic anemia, and acute kidney injury. HUS usually occurs in children... read more is a serious complication that develops in 5 to 10% of STEC cases (and in 10 to 15% of O157:H7 cases), most commonly among the young and old.
Enterotoxigenic E. coli produces two toxins (one similar to cholera toxin) that cause watery diarrhea. This subtype is the most common cause of traveler’s diarrhea Traveler’s Diarrhea Traveler’s diarrhea is gastroenteritis that is usually caused by bacteria endemic to local water. Symptoms include vomiting and diarrhea. Diagnosis is mainly clinical. Treatment is with ciprofloxacin... read more in people visiting low- and middle-income countries.
Enteropathogenic E. coli causes watery diarrhea. Once a common cause of diarrhea outbreaks in nurseries, this subtype is now rare.
Enteroinvasive E. coli causes bloody or nonbloody diarrhea, primarily in low- and middle-income countries. It is rare in the US.
Enteroaggregative E. coli causes diarrhea of lesser severity but longer duration than the other subtypes. As with some of the other subtypes, it is more common in low- and middle-income countries and can be a cause of traveler's diarrhea.
Other strains of E. coli are capable of causing extraintestinal infection (see Escherichia coli Infections Escherichia coli Infections The gram-negative bacterium Escherichia coli is the most numerous aerobic commensal inhabitant of the large intestine. Certain strains cause diarrhea, and all can cause infection when... read more ).
(See also Overview of Gastroenteritis Overview of Gastroenteritis Gastroenteritis is inflammation of the lining of the stomach and small and large intestines. Most cases are infectious, although gastroenteritis may occur after ingestion of drugs and chemical... read more .)
Symptoms and Signs of E. coli Gastroenteritis
Symptoms of hemorrhagic E. coli are severe abdominal cramps which begin suddenly along with watery diarrhea, which may become bloody within 24 hours. The diarrhea usually lasts 1 to 8 days. Fever is usually absent or mild but occasionally can exceed 102° F (39° C).
Diagnosis of E. coli Gastroenteritis
Sometimes stool testing
Stool studies are not needed in most cases of acute diarrhea because they have a viral cause and are self-limited. Stool studies for a bacterial cause are indicated in patients with bloody or heme-positive stool, fever, moderate to severe diarrhea, or diarrhea lasting more than 7 days, in those 70 years old or older, or in those with inflammatory bowel disease or immunocompromising disorders such as HIV/AIDS. Stool studies are also indicated for those at high risk of spreading disease to others (eg, health care, day care, or food service workers), and during known or suspected outbreaks.
Each of the E. coli subtypes can be detected in stool by polymerase chain reaction (PCR) testing, typically using a multiplex PCR panel. Sometimes more than one organism is detected simultaneously, the clinical significance of which is unclear.
A rapid stool assay for Shiga toxin or, when available, a test for the gene that encodes the toxin may be helpful.
Treatment of E. coli Gastroenteritis
Oral or IV rehydration
Supportive care including rehydration with fluids and electrolytes is the mainstay of treatment and is all that is needed for most adults. Oral glucose-electrolyte solutions, broth, or bouillon may prevent dehydration or treat mild dehydration. Children may become dehydrated more quickly and should be given an appropriate rehydration solution (several are available commercially—see Oral Rehydration Oral Rehydration Oral fluid therapy is effective, safe, convenient, and inexpensive compared with IV therapy. Oral fluid therapy is recommended by the American Academy of Pediatrics and the World Health Organization... read more ). Isotonic IV fluids such as Ringer’s lactate and normal saline solution should be given when there is severe dehydration, shock, or altered mental status and failure of oral rehydration therapy or ileus (see also the Infectious Diseases Society of America's [IDSA] 2017 clinical practice guidelines for the diagnosis and management of infectious diarrhea). In severe dehydration, IV rehydration should be continued until pulse, perfusion, and mental status normalize.
Antidiarrheal agents (eg, loperamide) should not be given to children < 18 years of age with acute diarrhea (see the IDSA guidelines). Antidiarrheals are generally safe for adult patients with watery diarrhea (as shown by heme-negative stool). However, antidiarrheals may cause deterioration of patients with Clostridioides difficile or E. coli O157:H7 infection and thus should not be given to any patients with recent antibiotic use, bloody diarrhea, heme-positive stool, or diarrhea with fever, pending specific diagnosis.
The use of probiotics is not recommended for suspected E. coli gastroenteritis (see also the American College of Gastroenterology's 2016 clinical guideline of the diagnosis, treatment, and prevention of acute diarrheal infections in adults).
Antibiotics given empirically are generally not recommended except when suspicion of Shigella or Campylobacter infection is high (eg, contact with a known case). Otherwise, antibiotics should not be given until stool culture results are known because antibiotics increase the risk of hemolytic-uremic syndrome Hemolytic-Uremic Syndrome (HUS) Hemolytic-uremic syndrome (HUS) is an acute, fulminant disorder characterized by thrombocytopenia, microangiopathic hemolytic anemia, and acute kidney injury. HUS usually occurs in children... read more in patients infected with E. coli O157:H7. Stool culture results are particularly important in children, who have a higher rate of infection with E. coli O157:H7.
Different strains of E. coli can cause diarrhea by various mechanisms.
Enterohemorrhagic E. coli produces Shiga toxin, which causes hemorrhagic colitis and sometimes hemolytic-uremic syndrome; E. coli O157:H7 Infection by Escherichia coli O157:H7 and Other Enterohemorrhagic E. coli (EHEC) The gram-negative bacteria Escherichia coli O157:H7 and other enterohemorrhagic E. coli (EHEC) typically cause acute bloody diarrhea, which may lead to hemolytic-uremic syndrome... read more is the most common strain of this subtype in the US.
Stool testing is not needed routinely, but if an enterohemorrhagic strain is suspected, a rapid stool assay for Shiga toxin or gene-based testing should be done.
Antibiotics are generally not needed and can increase the risk of hemolytic-uremic syndrome when Shiga toxin–producing strains are involved.
Antidiarrheals are safe for adults with watery diarrhea but should be avoided in children < 18 years of age and in any patient with recent antibiotic use, bloody diarrhea, heme-positive stool, or diarrhea with fever.
The following are English-language resources that may be useful. Please note that THE MANUAL is not responsible for the content of these resources.
Infectious Diseases Society of America: 2017 Clinical practice guidelines for the diagnosis and management of infectious diarrhea
American College of Gastroenterology: 2016 Clinical guideline: Diagnosis, treatment, and prevention of acute diarrheal infections in adults