RÉSUMÉ
The use of natural products is crucial to suppress the development of these micro-organisms and to reduce the concentration necessary to inhibit these microrganisms, reducing the toxicity risks also. In this study, the essential oil from Chenopodium ambrosioides Leaves and its main constituent α-Terpinene were used in the antibacterial and potentiating activity of antibiotics and ethidium bromide assays, against the bacterial strains Staphylococcus aureus IS-58, carriers of efflux pumps. The Minimum Inhibitory Concentration (MIC) was determined using a microdilution method. The capacity of the aforementioned was also tested in combination with tetracycline and ethidium bromide, with the aim of improving the activity of the antibacterials. The MIC of the C. ambrosioides L. essential oil and of α-Terpinene were above 1024 µg/mL, comprising a clinically irrelevant value. However, when associated with the antibiotics, the C. ambrosioides L. essential oil, significantly decreased the MIC of tetracycline and ethidium bromide. The efflux pump is the only mechanism the bacteria possesses to reduce the toxicity of ethidium bromide, and thus this reduction in the MIC demonstrates that the C. ambrosioides L. essential oil is an effective option in the inhibition of the efflux pump present in these micro-organisms.