Evaluation of the combined effect of antibiotics and essential oils against Campylobacter multidrug resistant strains and their biofilm formation

Abstract

Introduction Campylobacter species are the first zoonotic pathogenic agents that are transmitted essentially to human via the consumption of contaminated food from animal origin. Aims The aim of the current work was to evaluate the Origanum compactum Benth, Rosmarinus officinalis L., Mentha pulegium L., and Lavandula stoechas L., essential oils antibacterial activity against 11 multidrug resistant strains of Campylobacter spp., study the synergistic effect of two essential oils in combination with two antibiotics and examine the capability of Campylobacter strains to produce biofilm. Material and methods The antibacterial activity of the four tested essential oils was evaluated using agar well diffusion and micro-dilution broth methods. These strains were also subjected to detection of biofilm and combinatory assay of essential oils and antibiotics using crystal violet and broth micro-dilution techniques respectively. Results The results showed that Campylobacter multidrug resistant strains were highly sensitive to O. compactum, M. pulegium and L. stoechas essential oils, in which the smallest MIC value noticed was 0.063% (v/v). The examined microorganisms formed moderate to strong biofilm biomass at 42 °C under aerobic conditions in nutriment broth and the pellicles formation was also observed in microaerobic environment. Our findings allow us to suggest that the main pure bioactive chemotypes of O..compactum, M. pulegium and L. stoechas essential oils may have an impressive inhibitory impact on Campylobacter strains that produce biofilm. To the best of our knowledge, this is the first in vitro report about combinatory effect of essential oils and antibiotics against Campylobacter spp. A high synergism was achieved with L. stoechas and O. compactum in combination with tetracycline or ampicillin, in which effective doses of EOs, ampicillin and tetracycline were reduced. No antagonistic effect was noticed in the strains tested. Nonetheless, the isolation of the main bioactive compounds of L. stoechas and M. pulegium need to be assessed, ex-vivo and in vivo, in order to fully elucidate the mechanism of action of these antimicrobial particles. Conclusion O. compactum and L. stoechas essential oils can be used alone or in mixtures to control Campylobacter spp. in food industries, farms, human and veterinary medicine.