‘Friendly’ E. coli may protect the gut from their deadly cousin
Written by James Kingsland on July 19, 2020 — Fact checked by Eleanor Bird, M.S.
A study suggests that a harmless strain of Escherichia coli called Nissle 1917 primes the small intestine to defend itself against another strain that causes potentially fatal infections.
Share on Pinterest‘Nissle did not kill pathogenic E. coli but rather ramps up your intestinal responses and prepares you for possible pathogens attacking the intestine,’ says the lead author of the new study.
Most strains of the bacterium E. coli are benign, but some can cause severe illness, including stomach cramps, vomiting, and diarrhea. The bacteria can spread via contaminated food and water or through contact with an animal or person who has the infection.
Other strains can cause urinary tract infections, respiratory illness, and pneumonia.
Some of the most dangerous E. coli strains produce a toxin called Shiga. In the United States, the Centers for Disease Control and Prevention (CDC) estimate that these strains are responsible for 265,000 infections annually.
They note that a strain called E. coli O157 causes about 36% of these infections. E. coli O157 can infect people of all ages, but infections can be particularly severe, and even fatal, in younger children.
Antibiotics are unsuitable for treating these infections because they can provoke the bacteria to produce more Shiga toxin, which can trigger a potentially fatal kidney condition called hemolytic uremic syndrome.
“Right now, there is no cure for an E. coli infection,” says Alison Weiss, Ph.D., a professor at the University of Cincinnati College of Medicine, OH. “We can give individuals fluids, but [the infection] can be really deadly, and it would be really nice for us to figure out how to cure it.”
Weiss and her colleague Suman Pradhan, Ph.D., wondered whether a probiotic could prevent infections, based on observations dating back to the early 20th century.
First World War
For more than 100 years, doctors have used a “friendly” E. coli strain called Nissle to prevent and treat infectious diarrhea.
Alfred Nissle, a German physician and researcher, first isolated the strain from the feces of a soldier during the First World War.
In 1917, Dr. Nissle noticed that in contrast to his fellow soldiers, the man did not develop diarrhea during an outbreak of the highly contagious bacterial infection shigellosis.
More than a century later, the strain of E. coli that was named after Nissle is the active component of a probiotic called Mutaflor that doctors in Europe, Canada, and Australia use to treat infectious diarrhea, chronic constipation, and inflammatory bowel disease.
Research in mice in 2009 suggested that Nissle could also protect people against infection with E. coli O157.
However, Weiss and Pradhan were concerned that this strain could have adapted to cause disease in humans, while leading to only mild symptoms, if any, in mice.
Studies in mice may, therefore, be a poor indicator of how good Nissle is at protecting people.
To get a better idea, the researchers used human pluripotent stem cells to create human intestinal organoids, which are tiny living models of the small intestine.
Pluripotent stem cells are universal progenitor cells that, under the right conditions, can differentiate into any tissue in the body.
This ability meant that the researchers were able to ensure that the organoids contained all the major cell types that are present in the lining of the human intestine.
As in a real intestine, each organoid comprised a space or lumen that a single layer of cells (an epithelium) enclosed.