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The composition of the human gut microbiota is related to host health, and it is thought that dietary habits may play a role in shaping this composition. Here, we examined the population size and prevalence of six predominant bacterial genera and the species compositions of genus Bifidobacterium (g-Bifid) and Bacteroides fragilis group (g-Bfra) in 42 healthy Belgian adults by quantitative PCR (qPCR) over a period of one month. The population sizes and prevalence of these bacteria were basically stable throughout the study period. The predominant g-Bifid species were Bifidobacterium adolescentis and Bifidobacterium longum ss. longum, and the predominant g-Bfra species were Bacteroides vulgatus, Bacteroides uniformis, and Bacteroides ovatus. The Belgian gut microbiota data were then compared with gut microbiota data from 46 Japanese subjects collected according to the same protocol (Matsuki et al., Appl. Environ. Microbiol. 70, 167–173, 2004). The population size and prevalence of Bifidobacterium catenulatum group were significantly lower in the Belgian gut microbiota than in the Japanese gut microbiota (P < 0.001); however, the population size and prevalence of g-Bifid did not differ. This species-level qPCR analysis will be helpful for investigating the diversity of gut microbiota among ethnic groups. [Copyright &y& Elsevier]

Injection of a lethal dose of 5-fluorouracil (400 mg/kg) into mice induced an extraordinary increase in the levels of endogenous Escherichia coli in the intestine, systemic translocation of the bacteria to the liver, and loss of body weight. Daily administration of a fermented milk (0.2 ml) containing Bifidobacterium breve strain Yakult, B. bifidum strain Yakult, and Lactobacillus acidophilus strain Yakult (10[sup 8.5-9.5] CFU/ml) to mice for 7 days before and 9 days after 5-FU prevented the endogenous infection, whereas treatment of mice with water or unfermented milk did not lead to any significant protection against the infection. The levels of indigenous bifidobacteria in the intestinal contents decreased markedly with time after injection of 5-FU in the control groups, and this was associated with a marked decrease in the concentration of total short-chain fatty acids (SCFAs) and an increase in the pH on day 10 after 5-FU administration (pH: 7.3, SCFAs: 40 mM). Administration of fermented milk maintained the concentrations of the total SCFAs at the same levels as before 5-FU administration (120 mM) throughout the experimental period. The pH and concentration of acetic acid in the intestinal contents (pH: 6.7, AA: 90 mM) were found to suppress in vitro growth of an indigenous strain of E. coli These results suggest that the protective effect of oral administration of fermented milk against the endogenous E. coli infection resulted from prevention of any abnormal increase in E. coli levels via normalization of the 5-FU-induced disruption of the intestinal environment. [ABSTRACT FROM AUTHOR]