Escherichia coli, commonly referred to as E. coli, is a bacterium that predominantly resides in the human gastrointestinal tract.
E. coli exists in various strains, and while the majority are harmless or even beneficial, some can cause severe infections.
E. coli serves a dual role within the human body. As a commensal bacterium, it plays a crucial role in digestion and helps maintain a balanced gut microbiome. In this context, it’s a beneficial presence.
However, some strains of E. coli are pathogenic and can lead to infections. These infections can vary in severity, ranging from mild gastrointestinal discomfort to life-threatening conditions.
What is Escherichia coli?
Escherichia coli (E. coli) is probably the most studied species of all known bacteria, and as a consequence, an impressive amount of information is available about it.
This Gram-negative, rod-shaped, facultative anaerobic bacterium was first described by Theodor Escherich in 1885 (Lim et al., 2010) from which its name was derived.
E. coli can be found in the intestinal microflora of a variety of animals including man. However, not all strains of E.coli are harmless as some can cause debilitating and sometimes fatal diseases in humans as well as mammals and birds (Bélanger, 2011).
Most information available on E. coli relates to serotype O157:H7 since it is easily differentiated biochemically from other E. coli strains.
Escherichia coli species, especially the O157:H7 strain, can be very lethal and are also of great economic importance, as we will soon discover from this article.
People can be forgiven for underestimating the virulence of this very important bacterium because most strains of Escherichia coli are known to be harmless.
Can Escherichia coli kill?
Yes, Escherichia coli (E. coli) can be potentially dangerous and, in some cases, can lead to life-threatening complications.
While most strains of E. coli are harmless and naturally occur in the intestines of humans and warm-blooded animals, certain strains can cause severe illness and even death.
One particular strain of E. coli that is known to be dangerous is Escherichia coli O157:H7. This strain can cause severe stomach pain, bloody diarrhea, and kidney failure.
In some cases, it can lead to a life-threatening condition called hemolytic uremic syndrome (HUS), where the red blood cells are destroyed and the kidneys fail.
According to the Centers for Disease Control and Prevention (CDC), the O157:H7 strain is estimated to cause 73,000 illnesses, 2,200 hospitalizations, and 60 deaths annually in the United States of America alone (Mead et al., 1999).
It has also been reported that the annual cost of illness due to Escherichia coli O157:H7 infections was 405 million dollars, including lost productivity, medical care, and premature deaths, outbreaks and sporadic cases continue to occur.
Types of E. coli
E. coli is a very diverse species that comprises both commensal and pathogenic strains.
Though most strains of E. coli harmlessly colonize the gastrointestinal tract of humans and animals as normal flora, there are some strains that have evolved into pathogenic E. coli by acquiring virulence factors.
The bacteria that make these toxins are called “Shiga toxin-producing E. coli” or STEC for short. STEC bacteria live in the intestines of many animals and are usually transmitted to people when they eat foods contaminated with the bacteria.
Hence, by way of categorization, Escherichia coli can be divided into two types: pathogenic E. coli and non-pathogenic E. coli.
1. Pathogenic E. coli
Pathogenic E. coli strains can be further classified into intestinal diarrheagenic E. coli which causes diarrhea and extra-intestinal E. coli (ExPEC) which causes a wide range of illnesses in humans, such as neonatal meningitis, chronic urinary tract infections, septicemia, and hemolytic uremic syndrome.
The pathogenic variants can be facultative or obligate pathogens. The facultative bacteria are part of the intestinal tract and may act as opportunistic pathogens when outside of their natural habitat, causing various types of extra-intestinal infections. On the other hand, intestinal obligate
pathogenic variants cause infections in distinct conditions, from moderate diarrhea to more threatening cases, which may have a lethal outcome.
2. Non-pathogenic E. coli
Non-pathogenic E. coli strains are described as commensal E. coli and are present in the normal microflora of the intestine which is harmless hinders the growth of harmful bacteria and produces vitamins (Nataro and Kaper, 1998; Beauchamp and Sofos, 2010).
How do people get E. coli?
The most frequent route of transmission of E. coli infections is via the consumption of contaminated food and water (Rangel, 2005).
- This occurs through various contaminated foods including vegetables, different meat products, ground beef, and unpasteurized dairy products which are the main origin of significant outbreaks around the world (Heiman et al., 2015).
- E. coli is found in feces secreted by sheep, birds, cattle, bats, pigs, goats, and dogs. Cattle and sheep are the main reservoirs of E. coli, especially the O157:H7 strain serotype, and are also major sources of E. coli infections in humans.
- The fecal release of the E. coli O157:H7 strain can bring about illnesses in people through contact with water and soil contaminated with animal excrements (Van et al., 2020) or with animals (Lim, 2020).
- They can also be spread directly from person to person, particularly in child daycare facilities (Heuvelink, 2002) and on farms.
What are the symptoms of E. coli infection?
E. coli infection can be serious for healthy people of any age, but it is more likely to cause severe illness in the very young (those under age five), the elderly, and immune-compromised patients (Tarr, 1995). Some known symptoms of E. coli are:
- Diarrhea – this may range from mild and watery to severe and bloody ∙ Abdominal cramps
- Loss of appetite or nausea
- Fever
- Vomiting and dehydration
Some patients progress to bloody diarrhea or hemorrhagic colitis (HC) in 1–3 days.
In 5–10% of HC patients, the disease can progress to the life-threatening sequelae, hemolytic uremic syndrome (HUS), which is a type of kidney failure, or thrombocytopenic purpura (TTP), (Banatvala et al., 2001).
How to prevent E. coli infection
Workers in certain industries have a higher risk of infection. People working in places such as slaughterhouses, farms, hospitals, nursing homes, nursery schools, and food preparation locations are more susceptible to infection than the rest of the population.
As with many foodborne and waterborne communicable infections, the best measures to control E. coli infections are preventive. Several measures can be taken to reduce the risk of infection. These include:
- Proper cooking; ensure that all meats are cooked thoroughly before eating.
- Prevent contamination of food by separating raw meats from cooked food, and washing fruits and vegetables thoroughly, especially those that will not be cooked. ∙ good personal hygiene; washing hands with soap before handling, preparing, or serving food, and after handling raw meat.
- Proper cleaning and sanitation habits; ensure that utensils and counters are well washed with soap and water, and floors in high risks spaces are disinfected regularly.
- Drinking only pasteurized milk, juice, and cider.
- Avoid swallowing lake or pool water while swimming.
Treatment of E. coli infection
Most people recover after 5 to 7 days when it is a case of non-bloody diarrhea and may self-resolve without further complication.
However, around 5–10% of people with STEC O157 infection develop hemolytic uremic syndrome (HUS), a type of kidney failure and a life-threatening complication. Many people with HUS require dialysis; some suffer permanent kidney damage or die (Banatvala et al., 2001).
Always consult a physician when you fill ill. Early diagnosis is an absolute requirement for success in treating potentially life-threatening complicated E.coli infections.
What Next?
Understanding the potential risks associated with E. coli infections is crucial.
While some infections can be mild and self-limiting, others can lead to severe complications, especially in vulnerable populations.
Preventive measures play a significant role in reducing the risks associated with E. coli infections.
These measures include practicing good hygiene, ensuring food safety, and seeking prompt medical attention when symptoms of infection arise.
In healthcare settings, infection control practices are essential to prevent healthcare-associated infections, including those caused by E. coli.