Rhamnolipids and surfactin inhibit the growth or formation of oral bacterial biofilm

Abstract

AbstractBackgroundBacteria survive in various environments by forming biofilms. Bacterial biofilms often cause significant problems to medical instruments and industrial processes. Techniques to inhibit biofilm formation are essential and have wide applications. In this study, we evaluated the ability of two types of biosurfactants (rhamnolipids and surfactin) to inhibit growth and biofilm formation ability of oral pathogenic bacteria such asAggregatibacter actinomycetemcomitans,Streptococcus mutans, andStreptococcus sanguinis.ResultsRhamnolipids inhibited the growth and biofilm formation ability of all examined oral bacteria. Surfactin showed effective inhibition againstS. sanguinisATCC10556, but lower effects towardA. actinomycetemcomitansY4 andS. mutansUA159. To corroborate these results, biofilms were observed by scanning electron microscopy (SEM) and confocal microscopy. The observations were largely in concordance with the biofilm assay results. We also attempted to determine the step in the biofilm formation process that was inhibited by biosurfactants. The results clearly demonstrated that rhamnolipids inhibit biofilm formation after the initiation process, however, they do not affect attachment or maturation.ConclusionsRhamnolipids inhibit oral bacterial growth and biofilm formation byA. actinomycetemcomitansY4, and may serve as novel oral drug against localized invasive periodontitis.