What is Escherichia coli Infection?
Escherichia coli, or E. coli, is a type of bacteria usually found in our intestines and typically causes no harm. However, certain types of E. coli can make us sick, causing illnesses in the intestines and other parts of the body. There are hundreds of different types of E. coli, and the diseases they cause can range from minor, short-lived stomach upsets to more severe conditions like kidney failure and serious blood infections. What makes E. coli so dangerous is its ability to avoid our bodies’ natural defenses and become resistant to many common antibiotics.
This article breaks down E. coli infections into two groups: those that cause intestinal illnesses and those that cause illnesses elsewhere in the body.
For intestinal illnesses, the types of E. coli responsible are named based on their characteristics. These include enterotoxigenic E. coli (ETEC), enterohemorrhagic E. coli (EHEC), also known as Shiga toxin-producing E. coli (STEC) – this will be referred to as EHEC/STEC, enteroinvasive E. coli (EIEC), enteropathogenic E. coli (EPEC), and enteroaggregative E. coli (EAEC).
Illnesses that occur outside the intestines will be identified according to the particular disease they cause.
What Causes Escherichia coli Infection?
E. coli is a type of bacteria that naturally lives in our intestines and is also common on hospital and care facility floors. Inside our intestines, it’s harmless. However, when it’s found in places outside of our intestines, E. coli can cause various infections. These could include urinary tract infections, pneumonia, blood infections (bacteremia), and inflammation of the abdomen (peritonitis).
E. coli is also a major cause of infections in hospitals, including those linked to catheters and ventilators. In addition, E. coli can be found in soil, on vegetables, and in water, as well as in undercooked meats. Certain harmful types of E. coli can cause stomach illnesses when you eat them.
Risk Factors and Frequency for Escherichia coli Infection
E. coli is a bacterium that can cause illnesses in the intestines and in other parts of the body. The intestinal diseases can be caused by one of five types of E. coli. These types are known for their specific O and H antigens – O antigen determined by the chain of sugars present in the bacteria’s outer membrane, and H antigen determined by the bacterium’s tail-like structure.
- ETEC is one type of E. coli causing watery diarrhea. It’s typically found in countries with inadequate sanitation in their food and water. For a healthy person to fall ill, they would need to ingest roughly 100 million of these bacteria. ETEC is common in travelers and is a significant cause of dehydration sickness in infants and children in developing countries.
- EPEC is another type that can cause watery diarrhea in babies and young children, especially in variant-resource countries, and can lead to isolated incidents or widespread outbreaks. This illness can be contracted through ingestion and can also spread from person to person.
- EAEC is an E. coli type that causes acute and ongoing watery diarrhea in both developing and developed countries and is increasingly responsible for traveller’s diarrhea.
- EHEC/STEC is an E. coli that produces a toxin called Shiga-toxin. This type includes the O157:H7 variant and others. It has been the culprit in several outbreaks, caused by eating contaminated spinach, sprouts, lettuce, fruit, raw milk products, or undercooked beef. This bacterium can be found in ground beef and veggies that have been fertilized with contaminated manure, and in water polluted by runoff from these crops. Only a small quantity (102 CFU) is needed to cause illness. According to the World Health Organization, in 2014, there were about 2.8 million global cases of EHEC/STEC infections, with 3,137 cases reported in the US in 2019 alone. Children under five and adults over 60 are most prone to severe complications.
- EIEC is another type of E. coli, but cases of EIEC-induced diarrhea are less common due to the large amount of bacteria needed for infection. It is, however, often underestimated and can be picked up through consuming undercooked meats and polluted vegetables.
However, E. coli can also cause illnesses outside of the intestines, which is often due to bacteria from the gut spreading to other body parts or spreading in hospital and long-term care facilities. E. coli is the main bacteria causing non-intestinal illness in humans and can lead to a urinary tract infection, abdomen and pelvis infections, pneumonia, bacteremia, and meningitis, among others.
Signs and Symptoms of Escherichia coli Infection
Diagnosing an E. coli infection requires a thorough medical history and physical exam. Doctors will ask patients about when their symptoms began, how long they have lasted, and how severe they are. They’ll also want to know if anything makes the symptoms better or worse and if the patient has tried any over-the-counter medications. These questions help the doctors distinguish E. coli infection from other illnesses affecting the intestines.
It’s important for doctors to learn whether a patient’s diarrhea is watery or bloody, as this can provide a clue about the cause of illness. Questions about recent travel and dietary habits can further suggest E. coli as the source of the problem, especially since ETEC, a type of E. coli, is a common cause of traveler’s diarrhea. With E. coli, symptoms usually don’t start until more than 16 hours after eating contaminated food, while other bacteria can cause symptoms more quickly.
If a patient has symptoms that suggest an E. coli infection outside the intestines, doctors will ask about past infections and assess the possibility of drug-resistant bacteria. When a patient has symptoms like those of a bladder infection, it’s also essential to know whether any devices like urinary stents or catheters are in place.
In the physical examination, doctors assess the illness’s severity. If vital signs such as heart rate and temperature show a severe disease, the patient may need hospital care. Clinicians will check for dehydration signs by looking at the patient’s gum and skin hydration. They will listen to the patient’s heart and lungs and perform a focused exam. If the patient has symptoms in the gut and urinary tract, a complete abdominal exam is needed. If sepsis, a serious, body-wide response to infection, is suspected, the doctor will do a thorough physical evaluation.
Testing for Escherichia coli Infection
If a patient appears healthy but has been experiencing diarrhea, it’s usually not necessary for doctors to run routine laboratory tests since this condition often improves on its own. However, if the patient displays worrying signs or symptoms that suggest a more serious illness, tests can be helpful in confirming suspicions and deciding on the best treatment. If a patient shows signs of having an infection caused by a harmful kind of E. coli bacteria called EHEC/STEC, they should have a complete blood count (CBC) and a basic metabolic panel (BMP) done. The doctor may also order stool cultures, which involves testing a sample of the patient’s stool to identify the bacteria that’s causing the illness. This is especially important for patients whose diarrhea has been lasting unusually long, patients displaying systemic signs or symptoms (indications that the illness is affecting the entire body, not just the digestive system), and patients with dysentery (bloody diarrhea).
E. coli bacteria are identified by their ability to ferment lactose and produce indole, a type of chemical compound. Traditionally, their identity is confirmed by growing them on MacConkey agar, a special substance used to cultivate bacteria in a lab, that contains lactose. If indole is also produced as the bacteria metabolizes, it confirms the presence of E. coli. Furthermore, EHEC/STEC E. coli strains can ferment another type of sugar, called sorbitol. Therefore, by cultivating the bacteria on sorbitol-containing media, doctors can distinguish EHEC/STEC from other E. coli strains.
In mild cases of illness, molecular diagnosis (testing that identifies the specific genes or parts of DNA of a pathogen) is not required. However, when it is necessary, different types of E. coli can be identified via PCR-based assays, which is a technique used to amplify a segment of DNA. Different types of E. coli are distinguishable by the presence of specific genes. ETEC is found via its LT and ST genes, EPEC through detection of the pEAF plasmid or its encoded BFP factor, EAEC by detecting the AggR regulon. EHEC/STEC is identified via a nucleic acid amplification test (NAAT) for the Shiga toxin 1 and Shiga toxin 2, while EIEC can be detected via a NAAT of the lacY gene.
If the illness has spread beyond the intestines, samples of blood, urine or mucous from the respiratory system can be cultured to identify the presence of E. coli bacteria. This versatility is a significant cause for concern as many types of this bacterium have developed genes that resist antibiotics. For example, Extended-spectrum beta-lactamase (ESBL) E. coli resist most beta-lactamase antibiotics, a class of antibiotics that includes penicillins and cephalosporins. Additionally, carbapenemase-producing E. coli strains possess genes that make them resistant to carbapenems, a group of antibiotics that includes imipenem, ertapenem, and meropenem.
Treatment Options for Escherichia coli Infection
If you catch an intestinal sickness caused by E. coli bacteria, doctors usually begin treatment by managing the symptoms. Diarrheal illness, a common symptom of E. coli infection, can be very distressing. The first line of treatment typically involves rehydration and medication to reduce diarrhea. Oral rehydration therapy is usually recommended initially for all patients experiencing diarrheal illnesses, as long as they can handle drinking fluids. If they can’t, intravenous hydration may be required. Medications that slow down your gut movement, known as ‘antimotility agents’ (for example, bismuth-subsalicylate and loperamide), can be used to mitigate the discomforting symptoms.
Although antibiotics can kill bacteria, they usually aren’t the first choice of treatment for diarrheal illnesses caused by E. coli. This is mainly because they can sometimes cause harmful side effects and lead to antibiotic-resistant bacteria. However, in severe cases like having more than six instances of diarrhea per day, high fever, severe dehydration requiring hospital admission, or diarrhea lasting more than seven days, doctors might consider using antibiotics. Rifaximin, azithromycin, and ciprofloxacin are among the antibiotics typically recommended for E. coli-related diarrheal illnesses.
It’s important to note that certain antibiotics are not recommended for patients who are suspected to have EHEC/STEC strains of E. coli, especially children and older adults. This is because these antibiotics can increase the risk of hemolytic uremic syndrome, a severe illness that can result in kidney failure.
Rehydration therapy is also commonly prescribed for bloody diarrhea. However, for patients with dysentery-like symptoms, using antimotility agents may worsen the illness. Furthermore, antibiotics are not recommended for patients presumed to have strains like EHEC/STEC E. coli causing bloody diarrhea.
If the patient is found to be infected with EHEC/STEC, especially children under 12 years, they may need to be hospitalized to prevent the spread of infection and to closely monitor their condition. These patients are usually given intravenous hydration with isotonic fluids, and antibiotics are typically avoided due to the increased risk of more severe illness. Certain medications that may affect kidney function, like nonsteroidal anti-inflammatory drugs (NSAIDs), should also be avoided.
For extraintestinal illnesses caused by E. coli, the choice of antibiotic should depend on local data on susceptibility and resistance traits, called antibiograms. The decision between oral and intravenous antibiotics should be guided by the specific circumstances of the illness. Generally, extraintestinal E. coli infections can be treated with a variety of antibiotics. It’s important to note that E. coli can carry genes that make them resistant to certain medications, so the choice of antibiotic should be carefully considered based on the specific traits of the bacteria.
Remember, if you think you have an E. coli infection, consult with your healthcare provider to guide you through the right treatment plan.
What else can Escherichia coli Infection be?
There are different culprits behind intestinal diseases. The usual suspect behind diarrhea that has a lot of water is often viruses like norovirus and rotavirus. However, bacteria such as Staphylococcus aureus, Bacillus cereus, and Vibrio cholerae can also be the cause. In cases where the diarrhea is inflamed or bloody, other potential culprits could include:
- Shigella spp,
- Salmonella spp,
- Campylobacter jejuni,
- Yersinia enterocolitica.
It’s also worth noting that other illnesses not limited to the intestines can be caused by various viruses and bacteria, with the specifics depending on the nature of the illness.
What to expect with Escherichia coli Infection
Most cases of diarrhea, including those caused by E. coli, generally have a good outcome. E. coli infections leading to watery diarrhea usually resolve themselves. When antibiotics are needed, they can effectively treat the disease, and patients usually return to full health. However, for children who develop a specific condition known as HUS (hemolytic uremic syndrome) after an E. coli infection, the risk of serious health problems or even death is higher. Approximately 4% of children who develop HUS as a result of this E. coli infection could die, and an additional 5% could have severe long-term health problems like kidney failure or stroke. Another 20 to 30 percent might experience other health issues; but those who escape these effects usually recover fully within two weeks.
The situation is different for patients who develop E. coli infections beyond the digestive tract, or “extraintestinal” infections. Whether these patients recover well doesn’t strictly depend on the E. coli itself; it depends more on whether they have other health problems. For instance, one of the conditions E. coli can cause is spontaneous bacterial peritonitis (a sudden inflammation of the peritoneum, the thin layer of tissue that lines the inside of the abdomen), which can occur in patients with ascites (a condition where fluid builds up in the abdomen). Even with treatment, this condition carries up to a 4 percent risk of death. These patients often have other serious health conditions that can affect their recovery.
Possible Complications When Diagnosed with Escherichia coli Infection
When people experience diarrhea, they can become dehydrated more easily. But staying hydrated and getting treatment early can usually help to prevent this. Some lasting issues, like constant diarrhea and irritable bowel syndrome, can happen, but these aren’t very common. If a person gets diarrhea because of EHEC/STEC, there’s a risk they could develop a condition called hemolytic uremic syndrome. This risk is biggest in children under five and adults over 60.
The chances of getting HUS depend on different factors, including whether Stx genes are active. If Stx2 genes are active in an EHEC/STEC infection, the risk of getting HUS could be as much as 24%. Children with HUS caused by EHEC/STEC are most likely to have longer-term problems. As we said before, about 5% will get very serious kidney disease or have a stroke, and between 20 and 30% will experience other health issues like high blood pressure, protein in their pee, and a drop in the rate that their kidneys filter waste (glomerular filtration rate). The complications that go along with E. Coli infections outside of the gut (extraintestinal) depend on the specific disease, and we won’t be covering those in this review.
Possible Long-Term Problems:
- Constant diarrhea
- Irritable bowel syndrome
- Hemolytic uremic syndrome (HUS)
- High chances of HUS due to the activation of Stx genes
- End-stage renal disease
- Stroke
- High blood pressure
- Proteinuria (Protein in urine)
- Decrease in the kidney’s waste filtering rate (glomerular filtration rate)
Preventing Escherichia coli Infection
Getting sick from E. coli bacteria can be prevented by washing your hands regularly, washing fruits and vegetables well, and fully cooking meat. When you’re in places with poor sanitation, like some developing countries, you can avoid getting ill by only drinking clean, purified water and fully cooking your food. You should also clean any raw fruits and vegetables in the same clean water. If there’s a high risk of getting ill and it can’t be avoided (like if you have a weak immune system), you can take preventive antibiotics to lower your chances of getting sick. The International Society of Travel Medicine (ISTM) suggests that people who are at high risk of catching illnesses causing diarrhea and need antibiotic prevention should take medications known as rifaximin or bismuth-subsalicylate.
For rifaximin, you should take 200 mg 1-3 times a day for as long as your trip lasts, but not for more than two weeks. This is the first choice of treatment.
For bismuth-subsalicylate, the dosage is 524 mg every 30-60 minutes if needed, but not more than 8 doses in a 24 hour period. This is the second choice of treatment.
To reduce the risk of E. coli affecting other parts of the body (extraintestinal infections), the prevention is specific to the type of disease. Some preventative measures are using medical devices like catheters less to avoid urinary tract infections connected with catheter use. In the intensive care unit (ICU), following certain protocols can reduce risks. For instance, raising the head of the patient’s bed to 30 degrees can lower the chances of getting a lung infection (pneumonia) from a ventilator. Taking chemoprophylaxis can also reduce the risk of spontaneous bacterial peritonitis (SBP), an abdominal infection, in high-risk groups.
