In order to investigate the metabolism of bile acids of the mouse by intestinal microorganisms, isolation of the organisms responsible for the transformation of bile acids in the intestinal tract of conventional mice and their activity
in vivo in mono- or polycontaminated exgermfree mice were made.
Bacteroides,
Lactobacillus,
Enterococcus and
Clostridium perfringens isolated from the intestines of conventional mice converted conjugated bile acids into free acids both
in vitro and
in vivo, but
E. coli,
Staphylococcus and
Proteus did not. These microorganisms capable of converting conjugates distributed in the whole intestines, also in the cecum and upper small intestine. Among the resident intestinal microorganisms of mice, only
E. coli had the ability of converting cholic acid into 7-ketodeoxycholic acid. The role of exogenic microorganisms in the conversion of free bile acids were also investigated compared with resident intestinal flora. Many species of such exogenic bacteria as
Shigella,
Salmonella and
El Tor vibrio had no effect on the conversion of cholic acid. Some of pathogenic
E. coli converted cholic acid and some did not.
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