Novel effect of plant lectins on the inhibition of Streptococcus mutans biofilm formation on saliva-coated surface

Dental caries is caused by the disturbance in oral homeostasis, marked by a notable increase in the population of Streptococcus mutans. Lectins are a group of plant proteins that are capable of recognizing the glycoconjugates present on the bacterial surface. The aim of this study was to evaluate the effect of seven plant lectins on the growth and initial adhesion of S. mutans. Lectins of different carbohydrate specificities were isolated from plant sources by conventional methods of protein purification. The effect on growth of S. mutans was evaluated following CLSI guidelines. None of the lectins used in this study inhibited the bacterial growth and multiplication. The adherence and biofilm formation of bacteria to saliva-coated polystyrene plates was tested in the presence of plant lectins. All the plant lectins tested, inhibited both the adherence and biofilm in a concentration dependent manner. Confocal microscopy and scanning electron microscopy were employed to assess the biofilm formation in the presence of plant lectin (glucose/mannose-specific) at sub-minimal inhibitory concentrations. These evaluations revealed that lectins inhibited the clumping and attachment of S. mutans. Lectins tested here inhibited initial biofilm formation by S. mutans. Glucose/Mannose-specific lectin altered the adhesion arrangement of the bacteria on the saliva-coated surfaces. The plant lectins used in this study may offer a novel strategy to reduce development of dental caries by inhibiting the initial adhesion and subsequent biofilm formation of S. mutans.