http://gastroenterology.medscape.com/reuters/prof/2000/10/10.23/20001020scie006.html

Some Bifidobacterium Strains in Human Infant Gut Are Antimicrobial

WESTPORT, CT (Reuters Health) Oct 23 - Some bifidobacterium strains
found
in the gut of infants have antimicrobial properties, suggesting that
they could act as
a barrier against enteropathogens, according to a team of French and
Swiss
researchers.

Dr. Alain L. Servin, from the Institut National de la Sante et de la
Recherche
Medicale in Paris, and colleagues isolated 14 bifidobacterium strains
from human
infant stools and tested them for their antimicrobial activity.

Using a strain of Salmonella typhimurium as an indicator, two of the
strains, CA1
and F9, were found to have antimicrobial activity. These bifidobacterium
strains
reduced the viability of other bacterial strains, including Escherichia
coli,
Klebsiella pneumoniae, Yersinia pseudotuberculosis, Staphylococcus
aureus,
and Pseudomonas aeruginosa.

Further investigation showed that the two bifidobacterium strains
produced a
lipophilic molecule or molecules with a molecular weight of less than
3500 that
appeared to be responsible for the antibacterial activity.

Dr. Servin and colleagues used these two strains to colonize the
intestinal tract of
germ-free monoxenic mice, then challenged them with Salmonella
typhimurium a
week later. As they report in the October 18th issue of Gut, the
bifidobacterium
strains protected the mice against a normally lethal infection.

"Several bifidobacterium strains from resident infant human
gastrointestinal
microflora exert antimicrobial activity, suggesting that they could
participate in
the 'barrier effect' produced by the indigenous microflora," the
researchers
conclude. They note that bifidobacteria are the predominant intestinal
organisms
in breast-fed infants.

Gut 2000;47:646-652.

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