Molecular detection of the predatory bacterium Bdellovibrio bacteriovorus from dental biofilms

Introduction: The oral microbiome is a complex community whose composition results from multiple interactions among different microorganisms and with the host. Predatory prokaryotes are recognized as important balancing factors in different ecosystems. Among them Bdellovibrio bacteriovorus received special attention for its strong predatory behaviour against many human pathogens in the absence of any toxic or pathogenic effect, so that it was proposed as a live probiotic/antibiotic agent. This work aimed to evaluate if B. bacteriovorus is detected from samples of human oral and dental biofilm. Materials and Methods: Samples of oral and dental biofilm were obtained from 20 adults of both sexes and processed for extraction of metagenomic DNA, to be used as templates for B. bacteriovorus-specific PCR reactions. Specificity of amplification products was confirmed by sequencing. Results: All 20 dental biofilm samples and 12 of 20 (60%) oral biofilm samples were resulted PCR positive. The sequences of 17 of 32 PCR products (53.1%) showed 100% identity with the reference sequence; the sequences of 11 of 32 PCR products (34.4%) showed ≥99% identity, while the remaining 4 products (12.5%) showed identities ranging between <99% and ≥97%. Conclusions: This is the first survey specifically reporting the presence of B. bacteriovorus in the human oral cavity and suggests that bacterial predation is a relevant balancing factor for the oral microbiota. Demonstration that B. bacteriovorus is able to colonize the oral cavity gives strength to proposals of its use as a probiotic/antibiotic in the prevention/treatment of selected oral diseases.