E. Coli Infection: Causes, Symptoms, and Treatment

Escherichia coli (E. coli) bacteria are naturally present in the gut of warm-blooded animals, including humans.

Key takeaways:
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    E. coli are a group of common gut bacteria, only some of which cause disease.
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    Some E. coli types that naturally live in the gut can cause illness elsewhere in the body. These types most commonly cause urinary tract infections.
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    Other E. coli types infect the gut and cause diarrheal illness. The majority of these infections spread through contaminated water or food.
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    Symptoms and treatment of E. coli vary depending on the type and location of infection.

Most kinds of E. coli are harmless, and some are helpful. Others can cause traveler’s diarrhea, bloody diarrhea, urinary tract infections, or illness elsewhere in the body.

What is Escherichia coli?

E. coli, which stands for Escherichia coli, refers to a large and mostly harmless group of gut (digestive tract) bacteria. These bacteria normally live in the lower part of the gut, also known as the colon or large intestine, of healthy humans and other warm-blooded animals.

Some types of E. coli not only cause no harm to humans but are also beneficial. These types help with digestion and protect the body from harmful germs. However, other E. coli types can cause many human diseases, most commonly involving the urinary and digestive tracts.

The type of E. coli that most people are familiar with causes traveler’s diarrhea. Also known as enterotoxigenic E. coli (ETEC), this type makes a toxin in the stomach that causes people to lose lots of water through the intestines. Another type of E. coli known as enterohemorrhagic E. coli (EHEC) is mainly responsible for food poisoning outbreaks worldwide. EHEC destroys the stomach tissue, causing bloody diarrhea.

What causes E. coli infections?

Infections can occur due to E. coli types that are naturally present in the human gut or harmful E. coli types that enter the body through the mouth. E. coli types that usually cause no harm when growing in the gut can cause illness if they enter a body part where they don’t naturally grow. For example, if a person wipes from front to back after urinating or having a bowel movement, E. coli can enter the urethra, leading to urinary tract infections (UTIs).

E. coli types that infect the gut, leading to diarrheal illness (also known as food poisoning or bacterial gastroenteritis), are most often spread through food or water that has come in contact with feces (contaminated). They can also spread by putting hands that have come in contact with E. coli in the mouth. Specifically, these types of infections come from:

  • Eating undercooked ground beef, unpasteurized (raw) dairy products, or raw fruits and vegetables (especially leafy greens, lettuce, or sprouts).
  • Drinking untreated water.
  • Swallowing contaminated swimming water.
  • Drinking raw milk or juices (such as fresh apple cider).
  • Touching infected animals or their environment (especially cows, sheep, or goats).
  • Contact with the feces of infected people.

Who can get sick from E. coli?

Although anyone can get sick from E. coli, certain people have a greater risk of infection and are more likely to develop serious health complications. These people include:

  • Adults over 65 years old.
  • Children under 5 years old.
  • People with weak immune systems.
  • International travelers.

What symptoms occur with E. coli infections?

Symptoms of E. coli infection can range from mild to severe depending on the type of E. coli causing the infection and its location . In general, people with E. coli types that cause diarrheal illness (gastroenteritis) may experience the following symptoms:

  • Watery or bloody diarrhea depending on the E. coli type.
  • Stomach cramps.
  • Nausea.
  • Vomiting.

In some cases, E. coli infections may cause no symptoms, while the worst E. coli types may cause infections that lead to kidney damage or other life-threatening conditions.

How do you treat E. coli infections?

Treatment for E. coli infections depends on the E. coli type, the location of the infection, and the severity of the symptoms. For example, antibiotics can effectively treat E. coli infections outside the gut, such as UTIs. But antibiotics are typically not recommended for E. coli types that infect the digestive tract because they can cause complications and delay recovery.

Most E. coli infections that cause diarrheal illness don’t require medical attention and go away on their own within 5 to 10 days. However, drinking lots of water is essential to replace lost fluids and electrolytes. Getting lots of rest also helps recovery. Additionally, if severe dehydration occurs, it may be necessary to go to the hospital to receive IV fluids.

E. coli bacteria are usually harmless, but some types may cause disease. Types of E. coli that naturally exist in the gut can cause urinary tract infections when it infects that tissue or infections elsewhere in the body. Other E. coli types cause digestive tract infections, leading to symptoms such as watery or bloody diarrhea, stomach cramps, nausea, and vomiting.

If your symptoms are severe, you have bloody diarrhea, or you have diarrhea or vomiting that lasts more than a couple of days, contact your healthcare provider. Also, seek medical attention if you cannot drink enough fluids to prevent dehydration. Signs of dehydration may include little or no urination, intense thirst, a dry mouth, lightheadedness, or dark-colored urine.


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