Differences in the Distribution of Bifidobacterial and Enterobacterial Species in Human Faecal Microflora of Three Different (Children, Adults, Elderly) Age Groups

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Abstract
To determine if there is any change with age in the distribution of Bifidobacterium and Enterobacteriaceae species in human intestinal microflora, strains were isolated from a total of 54 samples of human faeces (15 children, 3-15 years old; 17 adults, 30-46 years old; 22 elderly, 69-89 years old). The bifidobacteria were identified at species level using a numerical phenotypic identification system developed on the Internet (http://kounou.lille.inra.fr) and DNA-DNA hyridization. The enterobacteria were identified using the API 20E system (Biomérieux, France). Escherichia coli was present in 93% of samples. Enterobacter and Klebsiella species were more frequently found in children while Proteusi and Providencia species were typically found in the elderly. The species Bifidobacterium longum was the most frequently species isolated in children and adults, whereas Bifidobacterium adolescentis was the most encountered species in the elderly. The distribution of B. adolescentis was significantly split between the children and the elderly age groups. There is a noticeable trend whereby Bifidobacterium pseudocatenulatum occurs more frequently in children than in the elderly. The species Bifidobacterium infantis, Bifidobacterium gallicum and Bifidobacterium angulatum have never been isolated, while Bifidobacterium breve has only been isolated on one occasion.