Molecular differentiation of Lactococcus lactis subspecies lactis and cremoris strains by ribotyping and site specific-PCR.

Twenty-five strains of Lactococcus lactis subspecies lactis and subspecies cremoris obtained from dairy industry and environmental collections were examined by 16S RNA automated ribotyping profiles and site-specific PCR (S-PCR). By automated ribotyping, the majority of strains were classified in accordance with phenotypic characterization, with the exception of one lactis (220) and two cremoris (BO32 and 140) strains. A complete differentiation of subspecies lactis and cremoris in agreement with conventional phenotypic methods was achieved by S-PCR with a set of site-specific primer pairs (PR1, RM4, and F3) designed particularly from a deletion region found in subspecies cremoris, but not in lactis. Therefore, S-PCR with primers (PR1, RM4, and F3) is a rapid and very sensitive method for the distinction of lactis and cremoris subspecies in dairy production.