β-Methyl-D-galactoside: the first potential prebiotic for oral health?

Objectives: It has been shown that several commensal bacteria can inhibit the growth of pathogenic bacteria and attenuate the associated inflammatory response. Nutritional stimulation of these, so called, “beneficial bacteria” via prebiotics might therefore provide a health benefit. Currently there are no known prebiotics for oral health. The aim of this study was to identify prebiotic substances that can selectively stimulate the growth of beneficial bacteria and thereby suppress the growth of oral pathogens.
Methods: Six oral pathogenic and 9 commensal/beneficial bacteria were screened for their ability to metabolize 95 different carbon substrates. The substrate demonstrating the best metabolically stimulatory effect on beneficial bacteria without stimulating the pathogenic species was further investigated. Growth curves and single species biofilms were established in order to verify and translate the metabolic stimulation to bacterial growth promotion and increased biofilm formation. The prebiotic effect was verified in dual-species growth and biofilm experiments containing beneficial and pathogenic bacteria. The experiments were analyzed using OD, crystal violet staining and vitality qPCR. Each experiment was repeated at least 3 times.
Results: β-Methyl-D-galactoside was identified as a potential prebiotic since it stimulated the metabolic activity (factor 7.7), growth (factor 2.0) and biofilm formation (factor 10.5) of Streptococcus salivarius without having any effect on the tested pathogens. The dual-species experiments showed clear reductions in the proportion of pathogens in both liquid culture assays and biofilm assays when β-Methyl-D-galactoside was added to the cultures.
Conclusions: Selective stimulation of beneficial bacteria in dual-species communities is thus possible at an in vitro level. Such stimulation results in a reduction of pathogens. These observations support the hypothesis that by nutritional stimulation of beneficial bacteria, a microbial community can be shifted towards a more health associated composition. β-Methyl-D-galactoside could be the first known oral prebiotic, if the data can be confirmed at multi-species levels.