Many probiotic Bifidobacteriaceacontains an active tetW that renders the cells resistant to tetracycline. This may present a risk of a horizontal transfer of functional antibiotic genes. The present invention relates to a method of obtaining novel tetracycline-sensitive strains of the genus of Bifidobacteriacea (Bifidobacterium sp.). In particular, the present invention relates to novel antibiotic-sensitive strains obtained from antibiotic-resistant probiotic strains and the use of such novel strains for the preparation of a food or feed product or a dosage form comprising viable organisms.