[Comparison of the implantation and metabolic activity of human and rat fecal flora administered to axenic rats].

Gnotobiotic rodents are increasingly used as a model for studying in vivo the characteristics of human colonic flora. However, the value of this model has been poorly assessed. In this study fecal bacterial flora provided either by a conventional rat (group RFR) or by man (group RFH) was administered orally to two groups of 6 germ-free rats. One month later, quantitative bacteriological analyses of feces revealed that bacterial populations were close to those of donors in both groups. The metabolic activity of the genuine flora was further compared in groups RFR and RFH with that of the implanted flora: a) concentrations of each fecal volatile fatty acid and of fecal bile acids were similar in conventional and RFR rats as well as the percentage of transformation of cholesterol into coprostanol (48 p. 100 and 54 +/- 5 p. 100 respectively; m +/- SD); b) similar concentrations of fecal volatile fatty acids were obtained from the human donor and RFH rats. Alpha, beta and omega muricholic acids absent in human donor's feces were found in RFH feces. Cholesterol transformation was lower in RFH rats (48 +/- 9 p. 100) than in man (85 p. 100); c) a single dose of lactulose (3 g/kg) increased breath hydrogen excretion in man but not in conventional or in RFR rats and RFH. Chronic lactulose ingestion (3 g/kg d.i.b. for 8 days) had no effect in conventional or RFR rats. Hydrogen excretion was decreased in man, whereas it was significantly increased in RFH rats.(ABSTRACT TRUNCATED AT 250 WORDS)