An isolated microorganism of the genus Lactobacillus, wherein said isolated microorganism binds to Streptococcus mutans in the presence of saliva at a pH range between 4.5 and 8.5, wherein the binding between said isolated microorganism and Streptococcus mutans is calcium-dependent and resistant to heat treatment at more than 95° C. for at least 20 minutes, and wherein said isolated microorganism is selected from the group consisting of the deposited strains L. paracasei DSM 16667, L. paracasei DSM 16668, L. paracasei DSM 16669, L. paracasei DSM 16670, L. paracasei DSM 16671, L. rhamnosus DSM 16672, and L. rhamnosus DSM 16673.