ANTIBACTERIAL EFFECT OF ESSENTIAL OILS ON BIOFILM-FORMING BACTERIA

Abstract

Objective: To evaluate the in vitro antibacterial activity of essential oils of Eucalyptus globulus - Eucalyptus (EO1), Eugenia uniflora L. - Surinam cherry (EO2) and Mentha piperita - Peppermint (EO3) on cariogenic bacteria. Methods: Minimum Inhibitory Concentration (MIC) of EOs was determined through the microdilution technique on Streptococcus mutans (ATCC-25175), S. salivarius (ATCC-7073) and S. mitis (ATCC903). It was used a plate containing 96 wells. In each well were inserted 10μL of inoculum (108CFU/mL), 100μL of Brain Heart Infusion Broth (HIMEDIA, Sao Paulo, Brazil) doubly concentrated and 100μL of essential oils in concentrations ranging from 5 to 0.039mg.mL-1. Chlorhexidine (60μg.mL-1) was used as a positive control. Besides that, were also conducted controls regarding bacterial growth and sterility of the culture medium used. The results were read after 24 hours by visual method, and it was observed the formation or non-formation of cellular clusters ("button") at the bottom of the plate’s well. Results: EO1 inhibited visible bacterial growth at a concentration of 5mg.mL-1 on the three bacteria under study. MICs of 0.625mg.mL-1 and 3.75mg.mL-1 were showed by EO2 against S. mitis and S. salivarius, respectively. EO3 exhibited MICs of 0.625mg.mL-1, 0.312mg.mL-1 and 1.25mg.mL-1 on S. mutans, S. mitis and S. salivarius, respectively. Conclusion: The essential oils evaluated showed antibacterial activity against the cariogenic strains tested.