COMPARISON OF THE ANTIBACTERIAL AND ANTI-BIOFILM EFFECTS OF CORIANDER AND GARLIC ESSENTIAL OILS WITH CHLORHEXIDINE ON STREPTOCOCCUS MUTANS AND LACTOBACILLUS ACIDOPHILUS

Dental caries and periodontal diseases are among the most prevalent infectious diseases in humans. Therefore, this study was conducted with the aim of comparing the antibacterial and anti-biofilm effects of coriander and garlic essential oils with 0.2% chlorhexidine against Streptococcus mutans and Lactobacillus acidophilus. In this research, two pathogenic bacteria, Streptococcus mutans and Lactobacillus acidophilus, were used. These bacteria were purchased from the Iranian Genetic Resource Bank. To prepare fresh cultures of the microorganisms, surface inoculation was performed on Blood Agar medium for each microbial strain one day prior to the microbiological tests. The suspension of the microbial strains was standardized based on the 0.5 McFarland turbidity standard (1.5×108 colony forming unit/mL). To quantify the biofilm-forming capacity in the isolates of the two aforementioned bacteria, the Microtiter Plate (MTP) method was employed. 180 of TSB medium containing 1% glucose was poured into the wells of the ELISA plate, and then 20 of the suspension of the studied bacteria, equivalent to the 0.5 McFarland standard, was added to each well (To reduce error, each isolate was considered in three repetitions and in three wells). After 48 hours of incubation, to remove unattached bacteria, they were washed with PBS buffer solution, and 120 of methanol was used to fix the attached bacteria. A significant difference was observed in the diameter of the inhibition zone for the bacterium Streptococcus mutans among the three essential oils of garlic, coriander, and 0.2% chlorhexidine. Furthermore, for the bacterium Lactobacillus acidophilus, a significant difference was observed among all three groups (garlic essential oil, coriander essential oil, and 0.2% chlorhexidine) with three replicates for each essential oil (x2 = 6 and P = 0.02). Both Streptococcus mutans and Lactobacillus acidophilus exhibited moderate biofilm formation intensity. Garlic essential oil at a concentration of 5 uL/mL coriander at a concentration of 0.31uL/mL and 0.2% chlorhexidine at a concentration of 1.25 uL/m caused a reduction in biofilm formation by 25%, 100%, and 50%, respectively. Based on the results obtained in our study, coriander can be introduced as one of the selected options for subsequent studies as a mouthwash candidate.