Comparison of the fecal microflora in rural Japanese and urban Canadians.

The fecal microflora of nine rural healthy Japanese and eight urban healthy Canadians was examined. The two populations ate typical Japanese and western diets, respectively. The numbers of eubacteria (P less than 0.01), bifidobacteria (P less than 0.05), bacilli (P less than 0.01), lactobacilli and veillonellae and the frequency of occurrence of bifidobacteria were higher in the Japanese than in the Canadians. Higher numbers of bacteroides and lecithinase-negative clostridia were found in the Canadians. Twenty-three genera and over 75 species or biovars were isolated from the feces of Japanese and 18 genera and over 66 species or biovars from the Canadians. The numbers of Bacteroides vulgatus (P less than 0.05), Clostridium coccides (P less than 0.001), and C. tertium (P less than 0.05) and the incidence of B. uniformis (P less than 0.01), C. innocuum (P less than 0.05), and Bacillus spp. (P less than 0.01) were significantly lower in the Japanese than in the Canadians. In contrast, the numbers of Eubacterium aerofaciens (P less than 0.001), and the incidence of Bifidobacterium adolescentis biovar b (P less than 0.01) and Bacillus subtilis (P less than 0.01) were significantly higher in the Japanese than in the Canadians. These findings suggest that significant reductions in anaerobic gram-positive bacilli and increased numbers of bacteroides and clostridia in the feces were induced by the intake of a western diet.