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.
What is E. coli?
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 Good, the Bad, and the Ugly of E. coli
The CDC says that E. coli is a diverse group of bacteria – some of it good (beneficial) and some of it bad (pathogenic):
- Beneficial E. coli: These strains reside naturally in our gut, contributing to essential functions like vitamin K synthesis and aiding in food digestion. They help maintain a healthy gut microbiota balance, preventing harmful bacteria growth.
- Pathogenic E. coli: These strains produce toxins that can cause various illnesses, including food poisoning, urinary tract infections (UTIs), and even pneumonia. Common examples include Shiga toxin-producing E. coli (STEC) and Enterotoxigenic E. coli (ETEC).
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.
Six Types of Pathogenic E. Coli
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:
- 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 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).
“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.
Where Can You Find E. coli?
E coli is widespread in our environment, and its presence doesn't necessarily indicate contamination. Here are some common locations:- Intestines of humans and animals: This is the natural habitat of most E. coli strains.
- Contaminated food and water: Improper handling of food, especially raw meat, vegetables, and unpasteurized milk, can lead to E. coli contamination. Contaminated water sources can also harbor harmful strains.
- Soil and manure: Animal waste can be a source of E. coli, which can then contaminate crops or water through improper sanitation practices.
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.”
How Do E. coli Infections Spread?
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:
- Unpasteurized (raw) milk.
- Unpasteurized apple cider.
- Soft cheese 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),” 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.”
Protecting Yourself from Harmful E. coli
Here is what you can do to protect yourself from harmful E. coli:
- Practice proper food hygiene: Wash hands thoroughly before and after handling food, cook meat to safe internal temperatures, and refrigerate leftovers promptly.
- Consume pasteurized dairy products: Pasteurization effectively eliminates harmful bacteria, including E. coli, from milk and other dairy products.
- Be mindful of water sources: Drink treated or bottled water, especially when traveling to areas with questionable water quality.
- Maintain good hygiene: Washing hands regularly, especially after using the restroom and before handling food, helps prevent the spread of bacteria.
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.
