The use of continuous flow systems for studying the metabolic activity of the hindgut microflora in vitro.

To investigate the involvement of bacterial enzyme activities in the biotransformation of xenobiotic compounds, we have developed a simulation of the rat hindgut microflora in vitro. This mixed bacterial population exhibits many similarities to the native rat flora, and the diversity of bacterial species and the activity of a number of hydrolytic and reductive enzymes (e.g. azoreductase, beta-glucosidase, beta-glucuronidase, nitrate reductase and nitroreductase) are reproduced in the culture at levels similar to those found in the large intestine. The flora have been found to respond to an anutrient (cyclamate) or to host products (bile acids) with changes in enzyme activity, and to metabolize the azo dye Brown HT to metabolites qualitatively similar to those found in the faeces after oral administration to the rat. The experiments demonstrate that the bacterial population of the large intestine of the rat may be successfully cultured in vitro and provides and alternative to animal studies for the investigation of foreign compound metabolism by the flora.