Molecular discrimination of new isolates of Bifidobacterium animalis subsp. lactis from reference strains and commercial probiotic strains

Fifteen new isolates from pig faeces were identified as Bifidobacterium animalis subsp. lactis by polymerase chain reaction (PCR) using primers specific for this subspecies. Ten of the isolates could be differentiated at strain level by randomly amplified polymorphic DNA (RAPD) analysis and pulsed-field gel electrophoresis (PFGE). These new strains were different from the type strain and other reference strains of this subspecies, and from all commercial dairy strains with probiotic functionality. Thus, possibly some of the isolates are potential candidates for new probiotic Bifidobacterium strains that can be unambiguously identified by RAPD-PCR and PFGE, which could be of interest for the food industry. In contrast, reference strains and commercial dairy strains revealed great genetic homogeneity, showing almost identical DNA fingerprints using RAPD-PCR and PFGE. Some reference strains and all commercial probiotic strains that had been originally designated as B. animalis or B. lactis have to be assigned to B. animalis subsp. lactis to be correctly labelled.