Inhibitory Effects of Bifidobacterium longum BB536 on Harmful Intestinal Bacteria

The inhibitory effects of human-derived Bifidobacterium longum BB536 on harmful intestinal bacteria were examined by co-cultivation of BB536 with each one of the following eight bacterial strains: Escherichia coli, Klebsiella pneumoniae, Clostridium clostridiiforme, C. perfringens, Bacteroides distasonis, B. fragilis, B. thetaiotaomicron a d B. vulgatus. In comparison with the results of mono-cultivation, BB536 inhibited both the growth of these putrefactive bacteria and their production of ammonia, and decreased the pH of the culture medium by producing lactic and acetic acids. Enzymatic assays showed that in BB536 the sorts of the enzymes involved in ammonia production (urease and amino acid deaminases) were rather few and their activities were weaker than observed in the harmful bacteria, whereas the activities of enzymes involved in ammonia assimilation (glutamine synthetase, glutamate synthase and glutamate dehydrogenase) were much higher in BB536 than in the putrefactive bacteria.