Antimicrobial and Anti-Biofilm Activities of Thymus fallax Essential Oil against Oral Pathogens

Abstract

Aim. Oral infections associated with a wide diversity of microorganisms, including bacteria and yeasts, occur frequently in humans, affecting the whole oral cavity and well-being. Oral pathogens easily grow and propagate in the oral cavity, leading to the formation of dental plaque on both soft and hard tissue. The oral cavity contains up to 700 different species of microorganisms, which Candida and Streptococci are the most common organisms. Oral diseases continue to increase despite the best efforts of the medical and scientific communities. During the past decades, drug resistance to common antibiotics used in the treatment of oral infections has been raised to high levels worldwide. To overcome such resistance, there is a growing tendency to use herbal medicine as alternative. This study was conducted to find out the chemical constitution of Thymus fallax (T. fallax) essential oil and to determine its antimicrobial and anti-biofilm efficacy against common oral pathogens. Materials and Methods. The chemical compositions of the essential oil distilled from T. fallax plants were analyzed using gas chromatography/mass spectrometry (GC/MS). Antimicrobial susceptibility testing against common Streptococcus, Enterococcus, Staphylococcus, and Candida strains was assessed by broth microdilution in 96-well plates as suggested by the Clinical and Laboratory Standards Institute (CLSI) methods. Biofilm growth and development were assessed using XTT reduction assay. Results. Based on the GC/MS test results, thymol (67.75%) followed by caryophyllene (E-) (7.27%) was the main component of this essential oil. T. fallax inhibited the growth of examined microbial pathogens at concentrations of 0.031-16 μL/mL. Also, the essential oil showed biofilm inhibition of greater than 95% in the concentration of 8 μL/mL against all tested bacterial strains as well as Candida albicans ( $p$ value < 0.05). Conclusions. Considering the significant antimicrobial activities of T. fallax, this essential oil has the potential to be used as further antimicrobial and anti-biofilm pharmaceutical products in the control and treatment of oral infections.