Dietary Supplement Plays an Important Role Against Escherichia coli Infection

A new study found that gut bacteria and a diet rich in the amino acid "tryptophan" play a protective role against Escherichia coli pathogens. Escherichia coli can cause severe stomach disorders, cramps, fever, intestinal bleeding, and kidney failure. The researchers, led by Pamela Chang, an assistant professor of immunology at the College of Veterinary Medicine, and Samantha Scott, a postdoctoral researcher in Chang's lab, used mice infected with Citrobacter rodentium, which is quite similar to E. coli, since some E. coli pathogens do not infect mice. They identified fewer pathogens and inflammation (a sign of an active immune system and infection) after feeding the mice a tryptophan-based diet. To demonstrate the role of gut bacteria, they gave the mice antibiotics, and found that the mice were infected with C. rodentium despite consuming tryptophan, confirming that the protection provided by tryptophan depends on gut bacteria. The study explains that gut bacteria break down dietary tryptophan, which is mostly found in animal products, nuts, seeds, whole grains, and legumes, into small molecules called metabolites. A few of these metabolites bind to a receptor on the epithelial (surface) cells of the gut, ultimately reducing the production of proteins used by E. coli to adhere to the intestinal lining, where it causes infection. The research team describes a previously unknown role of the DRD2 receptor, known as the dopamine receptor (a neurotransmitter) in the central and peripheral nervous systems, within the gastrointestinal tract. When E. coli fails to adhere to the gut, the pathogen moves benignly throughout the body and exits.