Effect of oregano essential oil on biofilms formed by staphylococci and Escherichia coli

Abstract

In the present study, it was aimed to investigate the effect of oregano (Origanum onites) essential oil (EO) on biofilm formation and established biofilm. Staphylococcus aureus (n=6), Staphylococcus lugdunensis (n=1), Staphylococcus haemolyticus (n=1), Staphyococcus sciuri (n=1) and Escherichia coli (n=1) were used as the test organisms. The crystal violet assay was used for assessing the growth of the biofilm on 96-well polystyrene microtitre plates. The minimum inhibitory concentration (MIC) was determined by broth dilution method as 0.05% (v/v) for staphylococci with the exception of Staph. sciuri (0.8%, v/v) and 0.1% (v/v) for E. coli. Oregano EO inhibited biofilm formation and eradicated established biofilm at MIC level. Subinhibitory concentrations of the EO reduced the level of biofilm formation of the test strains. Further investigations should be examined whether these observations extend to biofilms formed on other surfaces, particularly those found in food processing plants. The ability of biofilm-embedded microorganisms to resist clearance by antimicrobial agents points to the importance of a continuous search for novel agents. The use of oregano EO as a natural antimicrobial agent can be an effective alternative or a supplement for the control of microorganisms.