A nutritional supplement that plays an important role against E. coli infection

A new study found that gut bacteria and a diet rich in the amino acid tryptophan play a protective role against pathogenic Escherichia coli.

E. coli can cause severe stomach upset, cramps, fever, intestinal bleeding, and kidney failure. 

The researchers, led by Pamela Chang, an assistant professor of immunology in the College of Veterinary Medicine, and Samantha Scott, a postdoctoral researcher in Chang's lab, used mice infected with Citrobacter rodentium bacteria, which are very similar to E. coli, since some E. coli pathogens do not Infect mice.

They identified fewer pathogens and infections (a sign of an active immune system and infection) after feeding the mice a diet based on a tryptophan supplement.

To prove the role of gut bacteria, they gave mice antibiotics for the bacteria, and found that the mice developed C. rodentium infections despite eating tryptophan, confirming that the protection provided by tryptophan depends on gut bacteria.

The study shows that gut bacteria break down dietary tryptophan, which is found mostly in animal products, nuts, seeds, whole grains and legumes, into small molecules called metabolites.

A small number of these metabolites bind to a receptor on the epithelial (surface) cells of the intestine, ultimately reducing the production of proteins that E. coli uses to attach to the lining of the intestine where it causes infection.

The research team describes a previously unknown role in the gut for the DRD2 receptor, which is known as a dopamine (neurotransmitter) receptor in the central and peripheral nervous system.

When E. coli fails to attach to the intestine, the pathogen moves benignly through and out of the body.

The study was published in the journal Nature.