The new findings could pave the way for probiotics to be one day used as a way to battle foodborne illnesses that affect millions of people every year, said the US-based researchers writing in Cell Host & Microbe.
Led by Dr Manuela Raffatellu from the University of California at Irvine, USA, the research team reveal that the probiotic strain Nissle 1917 (obtained from Ardeypharm) competes for essential iron more efficiently than Salmonella.
As a result, the team noted that counts of Salmonella – requires a high level or iron in order to replicate at high levels – decrease in the gut when Nissle was administered during infection.
“By administering Escherichia coli strain Nissle 1917, which assimilates iron by similar mechanisms, we show that this nonpathogenic bacterium can outcompete and reduce S. Typhimurium colonization in mouse models of acute colitis and chronic persistent infection,” said Raffatellu and her colleagues.
"Although we focused on Salmonella, our findings suggest that this approach can be effective against other gut bacterial pathogens that need iron to grow," Raffatellu commented.
"By understanding how these 'bad bugs' get nutrients, we can further study methods to eradicate them."
The bacterial strain E. coli Nissle was originally isolated from a healthy soldier during a Shigella outbreak in 1917 under the hypothesis that a protective commensal strain must have colonized the gut of that soldier.
For almost 100 years since its isolation, the strain has been tested and used in a variety of clinical settings to aid in the treat gastrointestinal disorders – however, much like many probiotic strains, the exact molecular mechanisms behind its apparent beneficial activity are not well understood.
“A large focus of research on probiotics has been on their interactions with the immune system rather than their competition with other microbes,” noted Raffatellu and her team – adding that their research has now shown that for Nissle at least it appears to be the more efficient uptake of essential iron that brings about health benefits.
Based on previous research that suggesting Salmonella Typhimurium relies heavily on a high iron intake to grow and replicate in the gut, and knowledge that Nissle reduced infection rates; the team hypothesised that the probiotic may reduce such infections by competing for this iron.
“To test the hypothesis that iron uptake mechanisms are important for E. coli Nissle probiotic activity, we set out to examine the effect of administering wild-type (WT) E. coli Nissle or mutant derivatives deficient in iron uptake on the course of S. Typhimurium infection,” the team explained.
The team used a combination of in vitro growth analysis and animal data that modelled bacterial infections caused by Salmonella in order to test this hypothesis.
“Iron availability impacts S. Typhimurium growth, and E. coli Nissle reduces S. Typhimurium intestinal colonization by competing for this limiting nutrient,” the team confirmed
Source: Cell Host & Microbe
Published online ahead of print, doi: 10.1016/j.chom.2013.06.007
“Probiotic Bacteria Reduce Salmonella Typhimurium Intestinal Colonization by Competing for Iron”
Authors: Elisa Deriu,Janet Z. Liu, Milad Pezeshki, et al