Diversity of lactobacilli in the oral cavities of young women with dental caries

For nearly a century, lactobacilli (LB) in the oral cavity have been generally associated with dental caries. Here, we characterized the LB isolated from the saliva of 6 women with active caries using genetic-based taxonomical identification methods. From each subject, 30 isolates growing on Rogosa medium and presumed to be LB were analyzed. Of the 180 isolates, 176 were further characterized by biotyping, DNA melting points, DNA chromosomal fingerprinting, genotyping, and phylogenetic cluster assessment. We found a total of 30 unique genotypes of LB in the saliva of caries-active women, with each woman harboring between 2 and 8 distinct genotypes. Although Lactobacillus vaginalis, L. fermentum, and L. salivarius were found in 4 of 6 of the subjects, results from other studies using comparable methods show an entirely different array of LB associated with caries. These collective observations lead us to surmise that LB associated with dental caries are likely exogenous and opportunistic colonizers, arising from food or other reservoirs outside the oral cavity.