Study Finds How Probiotics Protect Against Pathogen Infection in The Gut
07 Mar 2016 --- A collaborative study by British researchers in East Anglia has indicated how certain probiotic bacteria can help reduce infection by pathogenic E. coli.
Previous clinical studies have suggested that certain probiotic bacteria could prevent pathogenic bacteria from infecting the human gut. In particular, one common type of bacteria found naturally in the gut, the lactobacilli, can protect infants from infection by enteropathogenic E. coli (EPEC) – a major cause of foodborne disease in infants worldwide. However, it is unclear exactly how this works.
To better understand the mechanisms of this protective effect, Dr Stephanie Schüller from the Institute of Food Research (IFR) and the University of East Anglia (UEA) in the UK looked in detail at how Lactobacillus reuteri, a well-studied gut bacterium, affected EPEC adherence to different human intestinal cells. Her group collaborated with IFR’s Dr Nathalie Juge, an expert in mucus which is secreted by cells lining the gut and providing a niche for commensal bacteria and a natural barrier against infection. A number of infectious or inflammatory diseases are associated with alterations in the mucus layer.
The researchers also worked with the Gastroenterology Department from the Norfolk and Norwich University Hospital on human small intestinal biopsies.
They found that L. reuteri can inhibit EPEC binding to the gut lining. The results varied across different cell types studied depending on whether they produced a mucus layer or not, highlighting the need to choose a suitable model system when studying these complex bacterial interactions.
Schüller explained further: “We found that adherence of L. reuteri to human intestinal epithelium was strain-specific, and the mucus-binding proteins CmbA and MUB (characterised previously by Dr Juge’s group) increased binding to both mucus-producing and mucus-deficient cell lines.”
“Further studies with two selected isolates demonstrated that L. reuteri can reduce EPEC infection by several mechanisms which include competitive exclusion at the mucus or epithelial level or via potential inhibition of EPEC microcolony dispersal and cell-to-cell spread.”
The effects also varied depending on the L. reuteri strain used. “These effects were strain-specific and dependent on the intestinal model system used, highlighting the need for a careful choice of experimental models when selecting potential probiotic strains,” Schüller noted.
This will have real connotations for the choice of potential probiotic strains for therapies or treatments – in particular for people with conditions where their gut mucus may be compromised.
Schüller concluded: “Alterations in the mucus layer have been reported in a number of infectious and inflammatory diseases, often facilitating bacterial access to the epithelial surface. Whether individuals present with a healthy or compromised mucus layer may therefore influence the rationale for selecting specific probiotic strains.”
