Antibacterial Activity of Melaleuca alternifolia (tea tree essential oil) on Bacteria of the Dental Biofilm

Abstract

Objective: To evaluate the antibacterial activity of tea tree EO on Streptococcus mutans (ATCC 25175), S. salivarius (ATCC 7073) and Lactobacillus rhaminosus (ATCC 9595). Material and Methods: The antibacterial activity of M. alternifolia EO was evaluated by the broth dilution method, by which minimum inhibitory and bactericidal concentrations (MIC and MBC) were determined. Serial dilutions range from 70243.90 μg/mL to 26.14 μg/mL. The MIC evaluation was performed in 96-well microplates, in which 100 μL of Brain Heart Infusion (BHI), 100 μL of the EO dilution and 5 μL of the inoculum (final concentration = 5x105 CFU/mL) were inserted. After 24 h of incubation, MIC was determined as the lowest concentration capable of inhibiting microbial growth, identified by the resazurin reaction (100 μg/mL). CBM was identified by the absence of subculture growths (50 μL) of dilutions equal to or greater than MIC. Tests were performed in triplicate and at three different times (n = 9). Pharmacological controls (0.05% and 0.12% Chlorhexidine), growth and sterility were used to validate the results. Results: The MIC of M. alternifolia compared to S. mutans, S. salivarius and L. rhaminosus was 1940.16 μg/mL, 3977.34 μg/mL and 3977.34 μg/mL, respectively. The MBC values were 70243.90 μg/mL, 3977.34 μg/mL and 34265.31 μg/mL, respectively. Conclusion: The essential oil of M. alternifolia presented antibacterial activity against the microorganisms evaluated when in high concentration.