The researchers took 14 strains of bifidobacteria from infant stool samples. These in turn were cultured and tested against a wide range of harmful bacteria, including those associated with gut infections.
Two strains, CA1 and F9, decreased the numbers of bacteria, prevented them entering other cells, and killed off a strain of salmonella. The two strains also colonised the intestinal tract of mice, protecting them against lethal infection with salmonella.
The bifidobacteria are thought to work in concert with the antibiotic proteins and enzymes released by specialized cells in the gut lining, so producing a barrier against infection.
Bifidobacteria are found in breast milk.
Bifidobacteria are found in breast milk and their level can be increased by eating more fibre-rich foods and "live" yoghurt.