Dental caries; an old disease with largely unknown microbiota

Dental caries has been associated with acidogenic and aciduric bacteria, particularly Streptococcus mutans. However, we and others have shown that 10% of subjects with severe dental caries do not have any detectable levels S. mutans. Objective: Identify all cultivable and not-yet-cultivated bacteria present in progressive dental caries. Material and methods: Five subjects with severe caries in permanent teeth and two healthy controls were analyzed. Plaque was collected from; intact enamel, white spot lesions, cavitated lesions, and deep dentin lesions. Sample DNA was extracted, purified 16S rRNA genes were amplified, cloned and transformed into Escherichia coli. Sequences were used to determine species identity or closest relatives. Results: 224 bacterial species were detected, of which over 60% were species not presently cultivable. Surprisingly, 62 new phylotypes were identified. Bacterial profiles of caries in secondary dentition varied from subject to subject. In subjects with S. mutans, additional species, e.g., Atopobium clone GW027 or lactobacilli, were present at significantly higher levels. Atopobium spp. have not previously been associated with caries. Subjects with no detectable S. mutans, had a predominance of lactobacilli, Bifidobacterium dentium or low pH non-mutans Streptococcus spp. Bacterial profiles of caries in the secondary dentition were far more diverse than those in primary dentition. Actinomyces and non-mutans Streptococcus spp. appeared to be involved in initiation of the disease. White spots and intact enamel sites in diseased subjects often did not have any detectable levels of S. mutans. Conclusions: The major part of the caries microbiota is uncultivable containing an abundance of unrecognized species. With low detectable levels or in absence of S. mutans, other species, e.g., Lactobacillus, Bifidobacterium, and Atopobium, dominate the microflora in caries progression. Identification of cultivable and not-yet-cultivated caries pathogens shows a complex microbiota that will provide new targets for caries intervention. Supported; DE09513, DE11443, DE10467, Omnii Products.