Isolation and characterization of the antibiotic-resistant strains of Bifidobacterium spp

The strains of Bifidobacterium spp. highly resistant to ƒÀlactams, macrolides, and aminoglycosides were isolated by using the gradient plate and broth culture methods with ampicillin, cephalexin, erythromycin, and kanamycin as selective agents. The biochemical characteristics, cell morphology, and antigenic structure of the mutants were similar to those of their original strains, except for the possession of antibiotic resistance. We think this is the first report on the existence of ƒÀ-lactamor macrolide-resistant strains from the genus Bifidobacterium .