Chemical Profile of the Essential Oil of Lippia Origanoides Kunth and Antibiotic Resistance-Modifying Activity by Gaseous Contact Method

Introduction: Lippia origanoides is an aromatic shrub used as a culinary seasoning, as well as for therapy of gastrointestinal and respiratory diseases in traditional medicine of Brazilian Northeast. This study aimed to evaluate the antibacterial and resistance-modifying activity of the essential oil of L. origanoides (EOLO) and one of the major compounds, carvacrol.Methods: EOLO was extracted by hydro distillation and carvacrol was obtained commercially. Multidrug-re-sistant Staphylococcus aureus and Acinetobacter baumannii strains were tested for its antibiotic susceptibility in the presence or absence of the EOLO or carvacrol by gaseous contact.Results: Chemical analysis of EOLO demonstrated the presence of thymol, carvacrol and p-cimene. Both EOLO and carvacrol were active against both Gram-positive and Gram-negative strains. Moreover, volatile compounds from EOLO, as well as volatile carvacrol were able to potentiate the antimicrobial activity of the polymyxin B and norfloxacin against S. aureus. Gaseous contact of EOLO and carvacrol enhanced the activity of piperacillin and cefepime against A. baumannii. S. aureus and A. baumannii are important etiological agents of respiratory infections. Therefore, inhalation of EOLO concomitant with the administration of the antibiotics tested could be a promising clinical application in the treatment of infections caused by resistant S. aureus and A. baumannii.Conclusions: Inhalation of EOLO could be used as a complementary procedure for potentiate the activity of conventional antibiotics in the treatment of respiratory infections caused by drug-resistant S. aureus and A. baumannii strains.