Improved Method for the Determination of Antimicrobial Activity of Essential Oils in Agar Medium

Abstract

Publication details, including instructions for authors and subscription information:ABSTRACT: The influence of the number of bacterial cells inoculated and the emulsifying agent used to disperse essential oils (EO) into the culture media on the measurement of the antibacterial activity of EO in an agar medium was determined. The results showed that EO (oregano, thyme and clove) were most effective as antimicrobial agents when the bacterial load was low. Minimum inhibitory concentrations (MICs) were found to vary as a function of the emulsifylng agent used. However, MICs obtained by dispersing EOs into 0.2% agar solution without the use of solvents and detergents were greatly reduced compared to when they were used. This demonstrates the fact that solvents and detergents often used in antimicrobial studies significantly decrease the antibacterial activity of EO.

Composition chimique et activités antibactériennes, antifongiques et antioxydante de l'huile essentielle dePelargonium asperumEhrh.exWilde des Comores

“…Les concentrations minimales inhibitrices (CMI) des huiles essentielles ont été déter-minées selon la méthode rapportée par Remmal et al (1993) et Satrani et al (2001). Du fait de la non-miscibilité des huiles essentielles à l'eau et donc au milieu de culture, une mise en émulsion a été réalisée grâce à une solution d'agar à 0,2%.…”

Antifungal potential of the Seed and Leaf Foeniculum vulgare Mill essential Oil in liquid and vapor phase against phytopathogenic fungi

“…The essential oil was dispersed as an emulsion in sterile agar suspension (0.2%) (Remmal et al, 1993) and added to PDA immediately before it was emptied into the glass Petri dishes (90×20 mm in diameter) at a temperature of 40-45°C.…”

Effect of Sealing and Tween 80 on the Antifungal Susceptibility Testing of Essential Oils

“…A large number of papers have reported the in vitro antifungal activity of essential oils in solution, but, little systematic investigation has been done on the effect of sealing in the assay of essential oils in the aqueous phase. Sealing has usually been done to determine the antifungal activity of essential oils in the vapor state (8,19).Surface active agents such as Tween 80 were frequently used to obtain homogeneous suspension of essential oils in aqueous media (3, 4), but contradictory results have been reported on the effect of emulsifiers: one weakening the bioactivity (13,25), and the other increasing (28) or having little effect on the bioactivity (5) but giving good reproducibility (4, 11). The effect of Tween 80 to date examined mainly using bacterial strains, but no filamentous fungus has been tested.…”

“…Surface active agents such as Tween 80 were frequently used to obtain homogeneous suspension of essential oils in aqueous media (3,4), but contradictory results have been reported on the effect of emulsifiers: one weakening the bioactivity (13,25), and the other increasing (28) or having little effect on the bioactivity (5) but giving good reproducibility (4,11). The effect of Tween 80 to date examined mainly using bacterial strains, but no filamentous fungus has been tested.…”