Antibiotic and Antibiofilm Activities of Salvadora persica L. Essential Oils against Streptococcus mutans: A Detailed Comparative Study with Chlorhexidine Digluconate

The use of organic components from plants as an alternative antimicrobial agent is becoming popular due to the development of drug-resistance in various pathogens. Essential oils from fresh (MF-1) and dried (MD-1) roots of Salvadora persica L. were extracted and benzyl isothiocynate was determined as their chief constituent using GC-MS and GC-FID. The antibiofilm and antimicrobial activities of MD-1 and MF-1 against Streptococcus mutans a dental caries causing bacteria were determined using multiple assays. These activities were compared with chlorhexidine digluconate (CHX) and clove oil, well known antimicrobial agents for oral hygiene. Essential oils demonstrated IC(50) values (10–11 µg/mL) comparable to that of CHX, showed a significant reduction (82 ± 7–87 ± 6%) of the biofilm formation at a very low concentration. These results were supported by RT-PCR studies showing change in the expression levels of AtlE, gtfB, ymcA and sodA genes involved in autolysis, biofilm formation and oxidative stress, respectively. The results presented in this study show the robust bactericidal and antibiofilm activity of MD-1 and MF-1 against S. mutans which is comparable to Chlorhexidine digluconate. Our results suggest that these essential oils can be as effective as CHX and hence can serve as a good alternative antimicrobial agent for oral hygiene.