E. coli! Just the very words bring to mind danger as the headlines warn us of E. coli outbreaks that have sickened people around the country and new studies highlight the risk of the Shiga toxin-producing E. coli bacteria known as STEC in undercooked burgers.
Escherichia coli, often abbreviated as E. coli, is a type of bacteria that has gained notoriety for causing foodborne illness – an outbreak in 1993 in Jack in the Box hamburgers caused 4 deaths – but not all E. coli strains are harmful.
In fact, most E. coli bacteria live peacefully in our intestines, aiding digestion and contributing to a healthy gut microbiome.
Let’s look closer at these bacteria that get a bad rap but play a crucial role in our health.
E. coli is a rod-shaped, single-celled bacterium commonly found in the intestines of warm-blooded animals, including humans.
German pediatrician Theodor Escherich discovered the bacteria in 1885 – thus the name Escherichia. The second name “coli” is derived from the colon, where the bacteria lives and grows.
While some strains are harmless or even beneficial, others can cause various illnesses depending on their specific characteristics.
“Most E. coli are harmless and actually are an important part of a healthy human intestinal tract,” says the Centers for Disease Control and Prevention (CDC). “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 contact with animals or persons.”
The CDC says that E. coli is a diverse group of bacteria – some of it good (beneficial) and some of it bad (pathogenic):
An FAQ published on E. coli in the American Society for Microbiology says to think of E. coli strains like dog breeds. All strains of E. coli are the same type of organism, but they may have somewhat different traits.
“Like dog breeds, different E. coli strains can mix with each other to produce new strains with a combination of traits. Scientists sort E. coli into different strains according to the particular set of marker compounds they carry on their surfaces (not unlike dogs’ different colors and textures of hair),” explains the FAQ.
The CDC says that 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:
“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,” explains the CDC.
So, where can we find the Shiga toxin-producing E. coli, or STEC for short?
The CDC says: “STEC live in the guts of ruminant animals, including cattle, goats, sheep, deer, and elk. The major source of human illnesses is cattle. STECs 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.”
Now we understand what E. coli bacteria is and where it is found. How does the bad bacteria – the STEC – get transmitted to cause infections?
The infections are spread via a method that most people would rather not think about: they happen when we swallow STEC – small amounts of human or animal feces.
“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,” says the CDC. “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:
“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),” says the CDC. “People have gotten infected by swallowing lake water while swimming, touching the environment in petting zoos and other animal exhibits, and eating food prepared by people who did not wash their hands well after using the toilet. Almost everyone has some risk of infection.”
Here is what you can do to protect yourself from harmful E. coli:
Remember, not all E. coli bacteria are bad, and some even play a vital role in our well-being.
By understanding the different types of E. coli and practicing safe hygiene habits, we can minimize the risk of encountering harmful strains and maintain a healthy gut environment.