E. coli is the name of a type of bacteria that lives in your intestines. Most types of E. coli are harmless. However, some types can make you sick and cause diarrhea. One type causes travelers' diarrhea. The worst type of E. coli causes bloody diarrhea, and can sometimes cause kidney failure and even death. These problems are most likely to occur in children and in adults with weak immune systems.

You can get E. coli infections by eating foods containing the bacteria. Symptoms of infection include

• Nausea or vomiting
• Severe abdominal cramps
• Watery or very bloody diarrhea
• Fatigue
• Fever

To help avoid food poisoning and prevent infection, handle food safely. Cook meat well, wash fruits and vegetables before eating or cooking them, and avoid unpasteurized milk and juices. You can also get the infection by swallowing water in a swimming pool contaminated with human waste.

Most cases of E. coli infection get better without treatment in 5 to 10 days.

The gram-negative rod Escherichia coli is a common member of the normal microbiota of the colon. Although the vast majority of E. coli strains are helpful commensal bacteria, some can be pathogenic and may cause dangerous diarrheal disease. The pathogenic strains have additional virulence factors such as type 1 fimbriae that promote colonization of the colon or may produce toxins. These virulence factors are acquired through horizontal gene transfer.

Extraintestinal disease can result if the bacteria spread from the gastrointestinal tract. Although these bacteria can be spread from person to person, they are often acquired through contaminated food or water. There are six recognized pathogenic groups of E. coli, but we will focus here on the four that are most commonly transmitted through food and water.

Enterotoxigenic E. coli (ETEC), also known as traveler’s diarrhea, causes diarrheal illness and is common in less developed countries. In Mexico, ETEC infection is called Montezuma’s Revenge. Following ingestion of contaminated food or water, infected individuals develop a watery diarrhea, abdominal cramps, malaise (a feeling of being unwell), and a low fever. ETEC produces a heat-stable enterotoxin similar to cholera toxin, and adhesins called colonization factors that help the bacteria to attach to the intestinal wall. Some strains of ETEC also produce heat-labile toxins. The disease is usually relatively mild and self-limiting. Diagnosis involves culturing and PCR. If needed, antibiotic treatment with fluoroquinolones, doxycycline, rifaximin, and trimethoprim-sulfamethoxazole (TMP/SMZ) may shorten infection duration. However, antibiotic resistance is a problem.

Enteroinvasive E. coli (EIEC) is very similar to shigellosis, including its pathogenesis of intracellular invasion into intestinal epithelial tissue. This bacterium carries a large plasmid that is involved in epithelial cell penetration. The illness is usually self-limiting, with symptoms including watery diarrhea, chills, cramps, malaise, fever, and dysentery. Culturing and PCR testing can be used for diagnosis. Antibiotic treatment is not recommended, so supportive therapy is used if needed.

Enteropathogenic E. coli (EPEC) can cause a potentially fatal diarrhea, especially in infants and those in less developed countries. Fever, vomiting, and diarrhea can lead to severe dehydration. These E. coli inject a protein (Tir) that attaches to the surface of the intestinal epithelial cells and triggers rearrangement of host cell actin from microvilli to pedestals. Tir also happens to be the receptor for Intimin, a surface protein produced by EPEC, thereby allowing E. coli to “sit” on the pedestal. The genes necessary for this pedestal formation are encoded on the locus for enterocyte effacement (LEE) pathogenicity island. As with ETEC, diagnosis involves culturing and PCR. Treatment is similar to that for ETEC.

The most dangerous strains are enterohemorrhagic E. coli (EHEC), which are the strains capable of causing epidemics. In particular, the strain O157:H7 has been responsible for several recent outbreaks. Recall that the O and H refer to surface antigens that contribute to pathogenicity and trigger a host immune response (“O” refers to the O-side chain of the lipopolysaccharide and the “H” refers to the flagella). Similar to EPEC, EHEC also forms pedestals. EHEC also produces a Shiga-like toxin. Because the genome of this bacterium has been sequenced, it is known that the Shiga toxin genes were most likely acquired through transduction (horizontal gene transfer). The Shiga toxin genes originated from Shigelladysenteriae. Prophage from a bacteriophage that previously infected Shigella integrated into the chromosome of E. coli. The Shiga-like toxin is often called verotoxin.

EHEC can cause disease ranging from relatively mild to life-threatening. Symptoms include bloody diarrhea with severe cramping, but no fever. Although it is often self-limiting, it can lead to hemorrhagic colitis and profuse bleeding. One possible complication is HUS. Diagnosis involves culture, often using MacConkey with sorbitol agar to differentiate between E. coli O157:H7, which does not ferment sorbitol, and other less virulent strains of E. coli that can ferment sorbitol.

Serological typing or PCR testing also can be used, as well as genetic testing for Shiga toxin. To distinguish EPEC from EHEC, because they both form pedestals on intestinal epithelial cells, it is necessary to test for genes encoding for both the Shiga-like toxin and for the LEE. Both EPEC and EHEC have LEE, but EPEC lacks the gene for Shiga toxin. Antibiotic therapy is not recommended and may worsen HUS because of the toxins released when the bacteria are killed, so supportive therapies must be used. Table summarizes the characteristics of the four most common pathogenic groups.

E. coli are mostly harmless bacteria that live in the intestines of people and animals and contribute to intestinal health. However, eating or drinking food or water contaminated with certain types of E. coli can cause mild to severe gastrointestinal illness. Some types of pathogenic (illness-causing) E. coli, such as Shiga toxin-producing E. coli (STEC), can be life-threatening.

Some wildlife, livestock, and humans are occasional carriers of pathogenic E. coli and can contaminate meats and food crops. Contamination is typically spread when feces come into contact with food or water. Human carriers can spread infections when food handlers do not use proper hand washing hygiene after using the restroom. Pets and petting zoos can also cause infections if the animals are contaminated with pathogenic E. coli.

Symptoms

People infected with pathogenic E. coli can start to notice symptoms anywhere from a few days after consuming contaminated food or as much as nine days later. Generally, the symptoms include severe stomach cramps, diarrhea, fever, nausea, and/or vomiting.

The severity or presence of certain symptoms may depend on the type of pathogenic E. coli causing the infection. Some infections can cause severe bloody diarrhea and lead to life-threatening conditions, such as a type of kidney failure called hemolytic uremic syndrome (HUS), or the development of high blood pressure, chronic kidney disease, and neurologic problems. Other infections may have no symptoms or may resolve without medical treatment within five to seven days.

Due to the range in severity of illness, people should consult their health care provider if they suspect that they have developed symptoms that resemble a(n) E. coliinfection.

At-Risk Groups

People of any age can become infected with pathogenic E. coli. Children under the age of 5 years, adults older than 65, and people with weakened immune systems are more likely to develop severe illness as a result of an E. coli infection. However, even healthy older children and young adults can become seriously ill.

Foods Linked to U.S. Outbreaks of E. coli?

Different types of E. coli tend to contaminate different types of foods and water. Previous U.S. outbreaks of pathogenic E. coli have included leafy greens, sprouts, raw milk and cheeses, and raw beef and poultry.

Shiga toxin-producing E. coli (STEC), including E. coli O157:H7, can be particularly dangerous. The primary sources of STEC outbreaks are raw or undercooked ground meat products, raw milk and cheeses, and contaminated vegetables and sprouts.

Preventing Foodborne Illness at Home

Consumers should always practice safe food handling and preparation measures, which include the following:

• Wash hands with warm water and soap for at least 20 seconds before and after handling raw foods.
• Wash the inside walls and shelves of the refrigerator, cutting boards, countertops, and utensils that may have contacted contaminated foods; then sanitize them with a solution of one tablespoon of chlorine bleach to one gallon of hot water; dry with a clean cloth or paper towel that has not been previously used.
• Wipe up spills in the refrigerator immediately and clean the refrigerator regularly.
• Always wash hands with warm soapy water following the cleaning and sanitization process.
• People with pets should take special care to avoid cross-contamination when preparing their pet’s food. Be sure to pick up and thoroughly wash food dishes as soon as pets are done eating, and prevent children, the elderly, and any other people with weak immune systems from handling or being exposed to the food or pets that have eaten potentially contaminated food.
• Consumers can also submit a voluntarily report, a complaint, or adverse event (illness or serious allergic reaction) related to a food product.

Advice for Restaurants and Retailers

If there is an E. coli outbreak, retailers, restaurants, and other food service operators should not sell or serve any implicated or recalled foods – including those that may have been frozen and stored during a suspected outbreak. If you cannot determine the source of your food, do not sell or serve it.

Retailers, restaurants, and other food service operators should always take steps to avoid the cross contamination of cutting surfaces and utensils through contact with potentially contaminated products.

• Wash hands with warm water and soap for at least 20 seconds before and after handling raw foods.
• Wash the inside walls and shelves of the refrigerator, cutting boards and countertops, and utensils that may have contacted contaminated foods; then sanitize them with a solution of one tablespoon of chlorine bleach to one gallon of hot water; dry with a clean cloth or paper towel that has not been previously used.
• Wash and sanitize display cases and surfaces used to potentially store, serve, or prepare potentially contaminated foods.
• Wash hands with warm water and soap following the cleaning and sanitation process.
• Conduct regular frequent cleaning and sanitizing of cutting boards and utensils used in processing to help minimize the likelihood of cross-contamination.

Escherichia coli (E. coli) bacteria normally live in the intestines of people and animals. Most E. coli are harmless and actually are an important part of a healthy human intestinal tract. However, some E. coli are pathogenic, meaning they can cause illness, either diarrhea or illness outside of the intestinal tract. The types of E. coli that can cause diarrhea can be transmitted through contaminated water or food, or through contact with animals or persons.

E. coli consists of a diverse group of bacteria. Pathogenic E. coli strains are categorized into pathotypes. Six pathotypes are associated with diarrhea and collectively are referred to as diarrheagenic E. coli.

• Shiga toxin-producing E. coli (STEC)—STEC may also be referred to as Verocytotoxin-producing E. coli (VTEC) or enterohemorrhagic E. coli (EHEC). This pathotype is the one most commonly heard about in the news in association with foodborne outbreaks.
• Enterotoxigenic E. coli (ETEC)
• Enteropathogenic E. coli (EPEC)
• Enteroaggregative E. coli (EAEC)
• Enteroinvasive E. coli (EIEC)
• Diffusely adherent E. coli (DAEC)

Shiga toxin-producing E. coli (STEC)

What are Escherichia coli?

Escherichia coli (abbreviated as E. coli) are a large and diverse group of bacteria. Although most strains of E. coli are harmless, others can make you sick. Some kinds of E. coli can cause diarrhea, while others cause urinary tract infections, respiratory illness and pneumonia, and other illnesses. Still other kinds of E. coli are used as markers for water contamination—so you might hear about E. coli being found in drinking water, which are not themselves harmful, but indicate the water is contaminated. It does get a bit confusing—even to microbiologists.

What are Shiga toxin-producing E. coli (STEC)?

Some kinds of E. coli cause disease by making a toxin called Shiga toxin. The bacteria that make these toxins are called “Shiga toxin-producing” E. coli, or STEC for short. You might hear these bacteria called verocytotoxic E. coli (VTEC) or enterohemorrhagic E. coli (EHEC); these all refer generally to the same group of bacteria. The strain of Shiga toxin-producing E. coli O104:H4 that caused a large outbreak in Europe in 2011 was frequently referred to as EHEC. The most commonly identified STEC in North America is E. coli O157:H7 (often shortened to E. coli O157 or even just “O157”). When you hear news reports about outbreaks of “E. coli” infections, they are usually talking about E. coli O157.

In addition to E. coli O157, many other kinds (called serogroups) of STEC cause disease. Other E. coli serogroups in the STEC group, including E. coli O145, are sometimes called “non-O157 STECs.” Currently, there are limited public health surveillance data on the occurrence of non-O157 STECs, including STEC O145; many STEC O145 infections may go undiagnosed or unreported.

Compared with STEC O157 infections, identification of non-O157 STEC infections is more complex. First, clinical laboratories must test stool samples for the presence of Shiga toxins. Then, the positive samples must be sent to public health laboratories to look for non-O157 STEC. Clinical laboratories typically cannot identify non-O157 STEC. Other non-O157 STEC serogroups that often cause illness in people in the United States include O26, O111, and O103. Some types of STEC frequently cause severe disease, including bloody diarrhea and hemolytic uremic syndrome (HUS), which is a type of kidney failure.

Are there important differences between E. coli O157 and other STEC?

Most of what we know about STEC comes from studies of E. coli O157 infection, which was first identified as a pathogen in 1982. Less is known about the non-O157 STEC, partly because older laboratory practices did not identify non-O157 infections. As a whole, the non-O157 serogroups are less likely to cause severe illness than E. coli O157, though sometimes they can. For example, E. coli O26 produces the same type of toxins that E. coli O157 produces, and causes a similar illness, though it is typically less likely to lead to kidney problems (called hemolytic uremic syndrome, or HUS).

Who gets STEC infections?

People of any age can become infected. Very young children and the elderly are more likely to develop severe illness and hemolytic uremic syndrome (HUS) than others, but even healthy older children and young adults can become seriously ill.

What are the symptoms of STEC infections?

The symptoms of STEC infections vary for each person but often include severe stomach cramps, diarrhea (often bloody), and vomiting. If there is fever, it usually is not very high (less than 101˚F/less than 38.5˚C). Most people get better within 5–7 days. Some infections are very mild, but others are severe or even life-threatening.

What is hemolytic uremic syndrome (HUS), a complication of STEC infections?

Around 5–10% of those who are diagnosed with STEC infection develop a potentially life-threatening complication known as hemolytic uremic syndrome (HUS). Clues that a person is developing HUS include decreased frequency of urination, feeling very tired, and losing pink color in cheeks and inside the lower eyelids. Persons with HUS should be hospitalized because their kidneys may stop working and they may develop other serious problems. Most persons with HUS recover within a few weeks, but some suffer permanent damage or die.

How soon do symptoms appear after exposure?

The time between ingesting the STEC bacteria and feeling sick is called the “incubation period.” The incubation period is usually 3-4 days after the exposure, but may be as short as 1 day or as long as 10 days. The symptoms often begin slowly with mild belly pain or non-bloody diarrhea that worsens over several days. HUS, if it occurs, develops an average 7 days after the first symptoms, when the diarrhea is improving.

Where do STEC come from?

STEC live in the guts of ruminant animals, including cattle, goats, sheep, deer, and elk. The major source for human illnesses is cattle. STEC that cause human illness generally do not make animals sick. Other kinds of animals, including pigs and birds, sometimes pick up STEC from the environment and may spread it.

How are these infections spread?

Infections start when you swallow STEC—in other words, when you get tiny (usually invisible) amounts of human or animal feces in your mouth. Unfortunately, this happens more often than we would like to think about. Exposures that result in illness include consumption of contaminated food, consumption of unpasteurized (raw) milk, consumption of water that has not been disinfected, contact with cattle, or contact with the feces of infected people. Some foods are considered to carry such a high risk of infection with E. coli O157 or another germ that health officials recommend that people avoid them completely. These foods include unpasteurized (raw) milk, unpasteurized apple cider, and soft cheeses made from raw milk. Sometimes the contact is pretty obvious (working with cows at a dairy or changing diapers, for example), but sometimes it is not (like eating an undercooked hamburger or a contaminated piece of lettuce). People have gotten infected by swallowing lake water while swimming, touching the environment in petting zoos and other animal exhibits, and by eating food prepared by people who did not wash their hands well after using the toilet. Almost everyone has some risk of infection.

Where did my infection come from?

Because there are so many possible sources, for most people we can only guess. If your infection happens to be part of the about 20% of cases that are part of a recognized outbreak, the health department might identify the source.

How common are STEC infections?

An estimated 265,000 STEC infections occur each year in the United States. STEC O157 causes about 36% of these infections, and non-O157 STEC cause the rest. Public health experts rely on estimates rather than actual numbers of infections because not all STEC infections are diagnosed, for several reasons. Many infected people do not seek medical care; many of those who do seek care do not provide a stool specimen for testing, and many labs do not test for non-O157 STEC. However, this situation is changing as more labs have begun using newer, simpler tests that can help detect non-O157 STEC.

How are STEC infections diagnosed and when should I contact my healthcare provider?

STEC infections are usually diagnosed through laboratory testing of stool specimens (feces). Identifying the specific strain of STEC is essential for public health purposes, such as finding outbreaks. Many labs can determine if STEC are present, and most can identify E. coli O157. Labs that test for the presence of Shiga toxins in stool can detect non-O157 STEC infections. However, for the O group (serogroup) and other characteristics of non-O157 STEC to be identified, Shiga toxin-positive specimens must be sent to a state public health laboratory.

Contact your healthcare provider if you have diarrhea that lasts for more than 3 days, or it is accompanied by high fever, blood in the stool, or so much vomiting that you cannot keep liquids down and you pass very little urine.

What is the best treatment for STEC infection?

Non-specific supportive therapy, including hydration, is important. Antibiotics should not be used to treat this infection. There is no evidence that treatment with antibiotics is helpful, and taking antibiotics may increase the risk of HUS. Antidiarrheal agents like Imodium® may also increase that risk.

Should an infected person be excluded from school or work?

School and work exclusion policies differ by local jurisdiction. Check with your local or state health department to learn more about the laws where you live. In any case, good hand-washing after changing diapers, after using the toilet, and before preparing food is essential to prevent the spread of these and many other infections.

How can STEC infections be prevented?

• WASH YOUR HANDS thoroughly after using the bathroom or changing diapers and before preparing or eating food. WASH YOUR HANDS after contact with animals or their environments (at farms, petting zoos, fairs, even your own backyard).
• COOK meats thoroughly. Ground beef and meat that has been needle-tenderized should be cooked to a temperature of at least 160°F/70˚C. It’s best to use a thermometer, as color is not a very reliable indicator of “doneness.”
• AVOID raw milk, unpasteurized dairy products, and unpasteurized juices (like fresh apple cider).
• AVOID swallowing water when swimming or playing in lakes, ponds, streams, swimming pools, and backyard “kiddie” pools.
• PREVENT cross contamination in food preparation areas by thoroughly washing hands, counters, cutting boards, and utensils after they touch raw meat. To learn more about how to protect yourself from E. coli, see CDC’s feature, E. coli Infection.

Symptoms of Shiga toxin-producing E. coli (STEC) infection vary for each person, but often include severe stomach cramps, diarrhea (often bloody), and vomiting. Some people may have a fever, which usually is not very high (less than 101˚F/38.5˚C). Most people get better within 5 to 7 days. Some infections are very mild, but others are severe or even life-threatening.

Most people with a STEC infection start feeling sick 3 to 4 days after eating or drinking something that contains the bacteria. However, illnesses can start anywhere from 1 to 10 days after exposure. Contact your healthcare provider if you have diarrhea that lasts for more than 3 days or diarrhea that is accompanied by a fever higher than 102˚F, bloody diarrhea, or so much vomiting that you cannot keep liquids down and you pass very little urine.

Hemolytic Uremic Syndrome (HUS)

About 5 to 10% of people who are diagnosed with STEC infection develop a potentially life-threatening complication known as hemolytic uremic syndrome (HUS). HUS develops about 7 days after symptoms first appear, when diarrhea is improving. Clues that someone is developing HUS include decreased frequency of urination, feeling very tired, and losing pink color in cheeks and inside the lower eyelids. People with HUS should be hospitalized because their kidneys may stop working and they may develop other serious problems. Most people with HUS recover within a few weeks, but some suffer permanent damage or die.

Escherichia coli (abbreviated as E. coli) are bacteria found in the environment, foods, and intestines of people and animals.

Most E. coli are harmless and are actually an important part of a healthy human intestinal tract. However, some E. coli can cause diarrhea, urinary tract infections, respiratory illness, bloodstream infections, and other illnesses. The types of E. coli that can cause illness can be transmitted through contaminated water or food, or through contact with animals or people.

What are Shiga toxin-producing E. coli?

Some kinds of E. coli bacteria cause disease when they make a toxin called Shiga toxin. The bacteria that make these toxins are called “Shiga toxin-producing E. coli,” or STEC for short.

How can I prevent a STEC infection?

• Know your chances of getting food poisoning. People with higher chances for foodborne illness are pregnant women, newborns, children, older adults, and those with weak immune systems, such as people with cancer, diabetes, or HIV/AIDS.
• Practice proper hygiene, especially good handwashing.
  • Wash your hands thoroughly after using the bathroom and changing diapers.
  • Wash your hands thoroughly before and after preparing or eating food.
  • Wash your hands thoroughly after contact with animals or their environments (at farms, petting zoos, fairs, even your own backyard).
  • Wash your hands thoroughly before preparing and feeding bottles or foods to an infant or toddler, before touching an infant or toddler’s mouth, and before touching pacifiers or other things that go into an infant or toddler’s mouth.
  • Keep all objects that enter infants’ and toddlers’ mouths (such as pacifiers and teethers) clean.
  • If soap and water aren’t available, use an alcohol-based hand sanitizer with at least 60% alcohol (check the product label to be sure). These alcohol-based products can quickly reduce the number of germs on hands in some situations, but they are not a substitute for washing with soap and running water.
• Food Safety VideoView Transcript Low Resolution Video
• Follow the four steps to food safety when preparing food: clean, separate, cook, and chill.

• Wash fruits and vegetables well under running water, unless the package says the contents have already been washed.

• Cook meats thoroughly:
  • To kill harmful germs, cook beef steaks and roasts to an internal temperature of at least 145°F (62.6˚C) and allow to rest for 3 minutes after you remove meat from the grill or stove.
  • Cook ground beef and pork to a minimum internal temperature of 160°F (70˚C).
  • Always use a food thermometer to check that the meat has reached a safe internal temperature because you can’t tell whether meat is safely cooked by looking at its color.
• Don’t cause cross-contamination in food preparation areas. Thoroughly wash hands, counters, cutting boards, and utensils after they touch raw meat.
• Avoid raw milk, unpasteurized dairy products, and unpasteurized juices (such as fresh apple cider).
• Don’t swallow water when swimming and when playing in lakes, ponds, streams, swimming pools, and backyard “kiddie” pools.