Resumo

Staphylococcus aureus is a common etiologic agent of infectious illnesses worldwide and it exhibit a strong tendency to acquire resistance to several antibiotics. Methicillin resistant Staphylococcus aureus (MRSA) is a common cause of hospital and community-acquired infections worldwide. The ability to potentiate the antibiotic activity by natural products, like plants, has been investigated with the aim of to increase the effectiveness of such drugs against multidrug-resistant microorganisms. Lippia origanoides H.B.K. (LOEO), Verbenaceae, is an aromatic plant commonly used as culinary seasoning and in traditional medicine as remedy for gastrointestinal disorders and respiratory diseases treatment. The essential oil obtained of LOEO and its major constituents, carvacrol and thymol, exhibited antigenotoxic effect in bacterial cells, showing that this plant can be an important source of compounds with application in cancer chemoprevention. Also, has been verified that it shows antioxidant activity and low toxicity [26, 27], as well as antimicrobial activity against several pathogen groups, including bacteria, fungi, virus and evolutionary forms of protozoa. In this study the essential oil of LOEO, Verbenaceae, was assayed for its modifying drug activity against a MRSA strain by microdilution method. A significant potentiating effect between this oil and the aminoglycosides tested was verified. The MIC values for neomycin and amikacin alone were 2500 and 788 µg/mL, respectively. These were reduced to 248 and 78 µg/Ml, respectively, when they were associated with the essential oil against MRSA strain. A similar synergism was observed when the oil was changed for chlorpromazine, an efflux pump inhibitor, suggesting the involvement of resistance mediated by efflux system. The results indicated that LOEO can be a source of secondary metabolites to be used in association with aminoglycosides in the antibiotic chemotherapy against illnesses caused by MRSA.