Effect of Lippia origanoides H.B.K. essential oil in the resistance to aminoglycosides in methicillin resistant Staphylococcus aureus

Abstract Introduction Methicillin resistant Staphylococcus aureus (MRSA) is a common cause of hospital and community-acquired infections worldwide. Methodology In this study the essential oil of Lippia origanoides H.B.K., Verbenaceae, was assayed for its modifying drug activity against a MRSA strain by microdilution method. Results 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 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. Conclusions The results indicated that L. origanoides H.B.K. can be a source of secondary metabolites to be used in association with aminoglycosides in the antibiotic chemotherapy against illnesses caused by MRSA.