ESSENTIAL OILS EFFECT IN COMBINATION WITH ANTIBIOTICS AGAINST STAPHYLOCOCCUS AUREUS ATCC 29213 BIOFILM SUSCEPTIBILITY

Staphylococcus aureus biofilm has been known as one inducing factor for the bacteria’s resistance to various antibiotics. One strategy which may increase the efficacy of the antibiotic is by combining the antibiotic therapy with antiinfective from natural resources. This research was evaluating the potency of three known antiinfective essential oil derived from leaves of Piper betle L., Ocimum basilicum L. forma citratum Back and Cymbopogon citratus L., in a combination with antibiotics i.e. chloramphenicol, streptomycin, and erythromicin towards S. aureus ATCC 29213. The essential oils were obtained by steam-hydrodistillation of the fresh raw materials. Microdillution technique combined with colorimetric was used to determine the biofilm inhibition. Crystal violet was used for biofilm staining of which the reading was performed on a microplate reader. Fractional Inhibitory Concentration Index (FICI) values was evaluated based on the comparison of % inhibitory obtained from the essential oils and the antibiotics in a single and in a combination. The essential oils alone has the PMIC₅₀ (planktonic) values as follows, 0.2% (P. betel), 0,3% (C. citratus) and 0.84% v/v (O. basilicum).  However, all essential oils has FICI values of > 2 indicates that instead of causing a synergistic effect, the essential oils seems to be antagonist to the antibiotics’ biofilm formation inhibition activities.