Bacterial resistance to antibiotics and the search for new alternatives to antibiotics are of great importance in human and animal health. The main aim of this study was to evaluate the antibacterial pharmacodynamic properties of the essential oil of oregano as well as those of its major component, carvacrol, on strains of avian Escherichia coli resistant to antibiotics of current use in poultry (Colistin and Enrofloxacin). These properties were evaluated using standard agar diffusion and macro-dilution techniques for determination of Minimum Inhibitory Concentration (MIC). The results obtained showed a potent activity of the two tested products in comparison with the two antibiotics used in this study, giving the largest inhibition diameters which ranged respectively from 8 to 40 mm and from 14 to 30 mm for oregano essential oil (HE) and carvacrol. This was confirmed by the determination of the MIC which was 0.0031 % for oregano HE and 0.0625 % for its active ingredient. These results lead us to conclude that the use of oregano oil could be a good alternative to the evolving bacterial resistance. However, it would be interesting to confirm these results on living organisms in order to evaluate in vivo effectiveness of oregano essential oil and its active ingredients.

Keywords: Essential oil of oregano, carvacrol, Escherichia coli, antibio-resistance, antibacterial activity, MIC, poultry.