| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 4512131 | Industrial Crops and Products | 2016 | 6 Pages |
•Antibacterial activity of Artemisia herba-alba and Cymbopogon citratus EOs and their ability to restore antibiotics efficacy have been investigated.•Active compounds of studied EOs could be substrates of the efflux pumps of tested strains.•Lipopolysaccharide is involved in the resistance to the active compounds of studied EOs in Salmonella strains.•Studied EOs can block efflux pumps and may be good candidates to develop new drugs able to restore antibiotic activity of some MDR Gram-negative bacteria.
Inhibition of bacterial efflux mechanisms has been investigated as a promising target to combat the bacterial resistance to antibiotics. The present work investigated the ability of Artemisia herba-alba and Cymbopogon citratus essential oils (EOs) to inhibit efflux pumps of some selected antibiotic-resistant Gram-negative bacteria. The chemical profiles of tested EOs were evaluated by GC–MS. The major constituents of the oils were chrysanthenone (47.0%), camphor (24.0%), and verbenone (7.2%) in A. herba-alba EO and geranial (46.3%), neral (35.2%), and geraniol (5.4%) in C. citratus EO. Antibacterial tests showed that these EOs had high antibacterial activity. This activity was significantly enhanced in the presence of an efflux pump inhibitor, phenylalanine arginyl ß-naphthylamide (PAßN). When combined with PAßN, the MIC values against EA27 and AG102 (strains overexpressing efflux pumps) were decreased 32-fold and >32-fold, respectively, for A. herba-alba, and 512-fold and 1024-fold, respectively, for C. citratus EO. The involvement of a lipopolysaccharide (LPS) structure in the resistance to the active compounds of the studied EOs was also demonstrated in Salmonella LPS deep-rough mutants. Moreover, the combination of A. herba-alba and C. citratus EOs, at a low concentration, reduced significantly chloramphenicol MIC 2–4-fold, 4-fold and 8–16-fold, respectively, for EAEP294 (deleted of AcrAB), EA27 and AG102. For Salmonella strains, all tested combinations recorded a gain greater than or equal to 64-fold. It was concluded that these EOs can alter efflux pump activity and may be good candidates for the development of new chemosensitizer drugs able to restore antibiotic activity of some drug-resistant Gram-negative bacteria.
