Revista Electronica De Veterinar

Résumé

The aim of this work was to test three experimental strains (isolated from the faeces of exclusively breast-fed babies: Bbv1, Bbv2 and BLE) and a reference strain (BLR) of bifidobacteria for their antagonistic capacity towards Bacillus cereus ATCC 9884. The antagonism of these strains was studied using two methods: one consisted of co-cultivating them at 37°C with B. cereus and the other of bringing the concentrated supernatant of their culture into contact with that of B. cereus at 37 and 6°C. The effect of a series of organic solvents on the inhibitory power of bifidobacteria strains towards B. cereus was also explored. The results obtained indicate that at 37°C, the concentrated supernatants from bifidobacteria cultures exert an antagonistic effect towards B. cereus that is much greater than that observed when bifidobacteria strains are co-cultured with the pathogen strain under study. At low temperatures (6°C), the inhibitory power of the concentrated supernatants of the bifidobacteria cultures on B. cereus is greatly reduced and spread out over time, since 48h of contact allows only 60% inhibition on average. The speed of inhibition of B. cereus by bifidobacteria supernatants also highlights this latency of action at 6°C. Organic solvents such as formaldehyde, chloroform, acetone, hexane, isobutanol, methanol and diethyl ether had no effect on the antagonism of the concentrated supernatants from the bifidobacteria cultures tested against this pathogenic germ. This suggests that these solvents do not denature protein substances with antagonistic (i.e. bacteriocin-like) activity.

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