Antibacterial activity of Baccharis dracunculifolia in planktonic cultures and biofilms of Streptococcus mutans

Abstract

Summary: Streptococcus mutans is an important cariogenic microorganism, and alternative methods for its elimination are required. Different concentrations of Baccharis dracunculifolia essential oil (EO) were tested to determine its minimal inhibitory concentration (MIC) in planktonic cultures, and this concentration was used in S. mutans biofilms. Additionally, we assessed the effect of a 0.12% chlorhexidine (CHX) and saline solution in S. mutans biofilms. The biofilms were grown in discs of composite resin for 48 h and exposed to B. dracunculifolia, CHX or saline solution for 5 min. The viability of the biofilms was determined by counting the colony-forming units per milliliter (CFU/ml) in agar, which was statistically significant (P < 0.05). The MIC of the B. dracunculifolia EO to planktonic growth of S. mutans was 6%. In biofilms of S. mutans clinical isolates, B. dracunculifolia EO (6%) and CHX resulted in reductions of 53.3–91.1% and 79.1–96.6%, respectively. For the biofilm formed by the S. mutans reference strain, the reductions achieved with B. dracunculifolia EO and CHX were, respectively, 39.3% and 88.1%. It was concluded that B. dracunculifolia EO showed antibacterial activity and was able to control this oral microorganism, which otherwise causes dental caries. Keywords: Streptococcus mutans, Baccharis, Biofilms, Dental caries