Bactericidal effects of three mint essential oils on Porphyromonas gingivalis in Planktonic and Biofilm cells

Abstract

Mentha cordifolia (kitchen mint), Mentha arvensis (Japanese mint) and Ocimum basilicum (common basil) are commonly used as ingredients in cooking recipes in Thailand. The studies on anti-Porphyromonas gingivalis both planktonic and biofilm states of their essential oils, are very limited. This study was carried out to evaluate the Minimum Bactericidal Concentrations (MBCs) of essential oils of these 3 mints against a periodontal pathogen, Porphyromonas gingivalis (Pg) strain W50, grown in planktonic and biofilm states. Agar disc diffusion method was used for antibacterial screening of 3 essential oils. The MBCs of the essential oils against Pg, planktonic and biofilm cells were determined using micro-broth dilution method in 96-well microtiter plates. Two fold dilutions of essential oils were performed in Schaedler Anaerobic Broth and incubated with planktonic and biofilm-grown Pg cells. The remaining viable bacterial cells were checked by spot test. All 3 essential oils showed strong bactericidal effects on Pg. The MBCs of Mentha cordifolia, Mentha arvensis and Ocimum basilicum against Pg planktonic cells were 0.821, 6.537 and 3.625 mg mL-1, respectively, while the MBCs against Pg biofilm cells were 6.568, 26.150 and 14.498 mg mL-1, respectively. Mentha cordifolia oil possessed the highest bactericidal activity. The Pg biofilms showed 4-8 times decreased sensitivity to the oils as compared with the Pg planktonic cells. In conclusion, all 3 mint-extracted essential oils showed anti-Pg activity of low MBCs. This suggested that they could be formulated as active ingredients in oral health care products. © 2013 Academic Journals Inc.