Effect of intestinal bacteria on formation of azoxymethane-induced aberrant crypt foci in the rat colon

The effect of intestinal bacteria on formation of azoxymethane (AOM)-induced aberrant crypt foci (ACF) and DNA adducts in the rat colon was investigated. Male Sprague-Dawley rats were administered cultures of Lactobacillus acidophilus, Bifidobacterium adolescentis, Bacteroides fragilis, Escherichia coli and Clostridium perfringens for five weeks and given injections of AOM at 15 mg/kg body weight at the first and second weeks. The number of ACF five weeks after the start of the experiment was decreased in the rats treated with the cultures or culture supernatants of L. acidophilus and C. perfringens. The half-life of O-6-methylguanine (O-6-meG;) in the L. acidophilus group was shorter than that in the GAM broth group. The half-life of 7-methylguanine did not differ among the groups. These results suggest that the metabolite(s) of L. acidophilus and C. perfringens inhibit(s) the ACF formation in rats treated with AOM and that the inhibitory effect of L. acidophilus is due to the enhanced removal of O-6-meG from the colon mucosal DNA. (C) 1997 Academic Press.