Exploration of the antimicrobial synergy between selected natural substances on Streptococcus mutans to identify candidates for the control of dental caries
Dental caries is caused by dental plaque, a community of micro-organisms embedded in an extracellular polymer matrix as a biofilm on the tooth surface. Natural products that are widely available could be used as an alternative or adjunctive anti-caries therapy. Sometimes, when two products are used together, they yield a more powerful antimicrobial effect than the anticipated additive effect. These synergistic combinations are often better treatment options because individual agents may not have sufficient antimicrobial action to be effective when used alone. Cranberries contain phenolic compounds like proanthocyanidins (PAC) that disrupt biofilm formation. Manuka honey has high concentrations of the agent methylglyoxal, which is cariostatic. Because these agents have varied modes of antimicrobial action, they show potential for possible synergistic effects when paired. Various cranberry extracts were tested pairwise with manuka honey or methylglyoxal by well-diffusion assays and 96-well checkerboard assays in the presence of Streptococcus mutans to test for synergy. Synergy was demonstrated in two of the cranberry extracts paired with manuka honey. The synergistic combinations found in this research thus can be considered as candidates for the formulation of a dentifrice that could be used to inhibit the formation of dental plaque and thereby avoid the development of caries. Significance and ImpactThe emergence of bacteria resistant to antimicrobial agents has led to a shortage of options when choosing effective treatment agents. Further, some antibiotics used at therapeutic doses can produce undesired side effects. However, by utilizing synergistic combinations of antimicrobial agents, the desired antimicrobial effects can often be produced without subjecting the patient to toxic or irritating doses of individual agents. Streptococcus mutans growth and biofilm formation is a major contributor towards dental caries. In this study, a synergistic combination of Manuka honey and cranberry extracts gives evidence that it can be used as an alternative or adjunctive anti-caries therapy.