Abstract

Gastrointestinal microflora highly impacts their host mainly by performing a great variety of metabolic activities, protecting the host from pathogenic colonization. Mother's milk is a prebiotic factor which stimulates bifidobacteria growth in vivo. All strains of bifidobacteria were isolated on MRS medium (in addition to 0.05% cystéine HCL and 2 mg/l of nalidixic acid) from different origins (breast-fed infant faeces and yoghurt (bifidus). The strains belong to the following species: Bifidobacterium longum, B. Bréve, B. bifidum. We studied the antagonist power of Bifidobacterium against enteropathogenes (S. aureus,Escherichia coli, P. aeruginosa, Salmonella. Sp), using agar diffusion method.  In vitroantagonism test showed that our strains were able to produce antagonistic substances against various pathogenic microorganisms. The activity was completely destroyed by the action of proteolytic enzymes, indicating that the biologically active portion is proteinaceous. These properties suggest that inhibitory substance is considered as "Bacteriocin’’; these results emphasize the importance of the antimicrobial activity ofBifidobacterium in the dairy industry. Additional tests are needed to determine the exact nature of the inhibitors.

Key words: Intestinal flora, antagonist activity, antimicrobial substances, organic acids, bacteriocins like, enteropathogenes, inhibiting pathogens.