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In vitro antimicrobial activity of essential oil of Cymbopogon citratus (lemon grass) on Streptococcus mutans biofilm

The present study aimed to investigate the effect of essential oil of lemon grass (LGO) on Streptococcus mutans biofilm developed in hydroxyapatite discs surface. Initially, the susceptibility of S. mutans to the LGO through the inhibition zone test in planktonic suspension and minimum inhibitory concentration (MIC) was investigated. To evaluate the effect of the essential oil in biofilms, hydroxyapatite discs were used to simulate the tooth surface. The biofilms of S. mutans were developed on the discs for 5 days and immersed daily in the following groups: G1 - immersion for 5 min in LGO to 0808 mg/ml (test group) and G2 – Brain Heart Infusion (BHI) 1% Sucrose (negative control). Then biofilms were counted for colony forming unit (CFU) and transformed into log10. The data were analyzed by ANOVA test with a P value <0.05. The susceptibility test was positive indicating inhibition of microorganisms and the MIC value was 0.04 mg/mL. As for biofilm results, it decreased the bacterial growth in G2 compared to G1 with a statistically significant difference (P <0.034). Considering the limitations of this study, it was concluded that the essential oil of lemon grass was effective in controlling bacterial growth in biofilms of Streptococcus mutans. 
 
 Key words: Phytotherapy, Cymbopogon citratus, Streptococcus mutans, biofilm, dental plaque.