Bacteria of the week: Escherichia coli
Escherichia coli (E. coli) are bacteria found in the environment, foods, and intestines of people and animals. E. coli are a large and diverse group of bacteria. Although most strains of E. coli are harmless, others can make you sick. Some kinds of E. coli can cause diarrhea, while others cause urinary tract infections, respiratory illness and pneumonia, and other illnesses.
Name meaning: Escherichia coli was named for Theodor Escherich, a German-Austrian pediatrician. Escherich isolated a variety of bacteria from infant fecal samples by using his own anaerobic culture methods and Hans Christian Gram’s new staining technique
Microbiology description: a facultatively anaerobic, Gram-negative, rod shaped bacterium
E. coli is one of the most well-known bacteria in the world and the species includes diverse strains of bacteria. Most of these strains are harmless and occur widely in nature as well as in the intestinal tracts of humans and other animals. These bacteria help synthesize vitamins K and B complex, and also assist in food digestion and absorption. However, some strains cause infections that can lead to serious consequences.
E. coli is also often used a model organism and has helped in the development of modern molecular biology due to it's relatively small genome and fast replication rates. (E. coli has only 4,400 genes compared to ~25,000 genes in human cells!)
E. coli and Disease:
Some strains of E. coli produce what's known as 'Shiga toxin". Shiga toxin makes you sick, and cause diarrhea. In North America the most common form that causes infections is E. coli O157:H7. Some types of STEC (Shiga toxin-producing E. coli) frequently cause severe disease, including bloody diarrhea and hemolytic uremic syndrome (HUS), which is a type of kidney failure.
Where does this bacteria come from?
STEC live in the guts of ruminant animals, including cattle, goats, sheep, deer, and elk. The major source for human illnesses is cattle. STEC that cause human illness generally do not make animals sick. Sources of illness related E. coli often come from contaminated, uncooked food such as raw beef, unpasteurized dairy products, and raw fruits and vegetables. Water can also be contaminated with E. coli. Working with and handling livestock, especially cattle, is an additional risk factor for contracting an E. coli related illness.
How can I protect myself from an E. coli related infection?
While not all E. coli are E. coli that will make you sick, the best way to protect yourself is, as always, washing your hands! Wash your hands thoroughly after using the bathroom or changing diapers and before preparing or eating food. Wash your hands after contact with animals or their environments (at farms, petting zoos, fairs, even your own backyard). Cook meats thoroughly! Ground beef and meat that has been needle-tenderized should be cooked to a temperature of at least 160°F/70˚C. Avoid unpasteurized dairy products.
E. coli is the reason you've always heard to not eat raw dough! The main reason why is actually flour, not eggs. (Raw eggs are linked with cases of salmonella, another diarrheal disease, not E. coli). Flour is actually raw food, even if it doesn't look it. The grains can get contaminated in the fields while growing, and before flour goes into the oven it has not been cooked, similar to raw meats. CDC investigated outbreaks of E. coli infections linked to raw flour or cake mix in 2016, 2019, and 2021.
Symptoms of E. coli infection include stomach cramps that can be severe, diarrhea (often bloody), and vomiting. People usually get sick 3 to 4 days after swallowing the germ and recover within a week. However, some people develop a serious illness called hemolytic uremic syndrome (HUS), which can result in kidney failure, stroke, and even death. Symptoms of Salmonella infection include diarrhea, fever, and stomach cramps. Symptoms start 6 hours to 6 days after swallowing the germ and go away within 4 to 7 days.
Hope you've enjoyed the bacteria of the week! E. coli are fascinating because some strains live peacefully in our intestines, and are actually required by our body to synthesize some vitamins we can't make, and other strains can kill us!
Signing off, stay healthy, and wash your hands!
