Fecal bacteria in South African rural blacks and other population groups.

Quantitative studies were performed on fecal flora of three population groups consuming different diets. Twenty rural black South Africans and 22 Japanese, representing groups at low risk for carcinoma of the colon, were compared with 41 North Americans from a high-risk population. Specimens taken immediately after defecation were mixed and processed under anaerobic conditions. After the initial incubation, roll tubes were shipped to the United States for final identification. Bacterioides and bifidobacteria were present in lower numbers in South African subjects, as were Bacteroides uniformis (thought to be increased by conditions of fear and anger stress), compared with the other two groups. The number of B. vulgatus and B. distasonis and the "Peptostreptococcus productus species complex," showed a positive correlation with the risk of colon cancer, while an inverse relationship was found with Eubacterium aerofaciens II, B. fragilis and Escherichia coli. The percentage of fecal isolates stimulated by bile was slightly higher in populations with a high fat intake and a high risk of cancer of the colon.