Antimicrobial activity of six essential oils against Burkholderia cepacia complex: insights into mechanism(s) of action

Aims:To investigate the activity and mechanisms of action of six Essential Oils (EOs) against Burkholderia cepacia complex, opportunistic human pathogens highly resistant to antibiotics. Materials & Methods:Minimal inhibitory concentration of EOs alone, plus antibiotics or efflux pump inhibitors was determined. Results; Origanum vulgare, Thymus vulgaris, and Eugenia caryophyllata EOs resulted to be more active than the other EOs. EOs did not enhance antibiotic activity against the model strain Burkholderia cenocepacia J2315. EOsresulted more active in the presence of an efflux pump inhibitor acting on RND (Resistance- Nodulation-Cell Division) efflux pumps and against B. cenocepacia J2315 RND knocked-out mutants. Conclusions:EOs showed intracellular mechanisms of action and,thus, the efflux pumps inhibitor addition could boost their activity.