Biohydrogenation of cholesterol as an index of bacterial 7 alpha-dehydroxylase activity.

Fecal steroid compositions of 82 human subjects of various ages and diets and gastrointestinal status were examined by gas liquid chromatography. Progressive increases in bacterial activities on both bile acids and neutral sterols were observed with the advance of age in infants and children. The patterns in the 4-year-olds approached those observed in adults. Bacterial activities on fecal steroids were found to be decreased in adult subjects with acute shigellosis and in those challenged by castor oil. In contrast, no significant changes in fecal steroid profiles were observed in the subjects with traveller's diarrhea associated with toxigenic Escherichia coli. The effects of diarrhea on fecal steroids of infants under 1 1/2 years were less consistent than those of adults. However, a close relationship was observed between the degree of 7 alpha-dehydroxylation of cholic acid (expressed as the ratio of deoxycholic to the sum of deoxycholic and cholic acids) and the percentage of cholesterol in the feces (r = -0.921, p less than 0.001). The correlation between the production of lithocholic acid and the percentage cholesterol was also good (r = -0.739, p less than 0.001). Analysis of neutral steroids may be a good index of intraluminal bile acid metabolism.