TABLE 4.
Synergistic effects of Essential oils and antibiotics against ESKAPE pathogens.
| EOs/EOC | Antibiotics | Bacterial strains | Method(s) | Outcome | Mechanism of action | References |
| Artemisia herba-alba Asso | Chloramphenicol | E. aerogenes EA27 | Microdilution method (MDM) | 4-fold reduction in MIC | Alteration of outer membrane (OM), lipopolysaccharide structure (LPS) | Fadli et al., 2016 |
| Aniba rosaeodora | Gentamicin | A. baumannii | Checkerboard assay (CBA) | FICI = 0.11 | – | Rosato et al., 2007 |
| Cymbopogon citratus (DC.) Stap | Chloramphenicol | E. aerogenes EA27 | MDM | 4-fold reduction in MIC | Alteration of OM-LPS | Fadli et al., 2016 |
| Cinnamomum zeylanicum | Amikacin | Acinetobacter sp., | CBA | Additive effect | – | Guerra et al., 2012 |
| Coriandrum sativum | Chloramphenicol, Ciprofloxacin, Gentamicin |
A. baumannii | CBA | FICI = 0.047 to 0.375 | – | Duarte et al., 2012 |
| Croton zehntneri Pax & K.Hoffm | Norfloxacin | S. aureus SA 1199B | Change in inhibition zone by EO gaseous contact (IZGC) | IZGC = 39.5% | Inhibition of efflux pumps activity/expression (IEPA/E) | Coutinho et al., 2010 |
| Helichrysum italicum (Roth) G.Don | Chloramphenicol | E. aerogenes EA27 | MDM | 8-fold reduction in MIC | IEPA/E | Lorenzi et al., 2009 |
| Helichrysum italicum (Roth) G.Don | Chloramphenicol | A. baumannii AP1 | MDM | 8-fold reduction in MIC | IEPA/E | Lorenzi et al., 2009 |
| Lippia microphylla Cham. | Norfloxacin | S. aureus SA 1199B | IZGC | IZGC = 39.5% | IEPA/E | Coutinho et al., 2011 |
| Myrtus communis | Ciprofloxacine, polymixin B | A. baumannii | CBA | FICI = 0.047–0.375 | – | Aleksic et al., 2014 |
| Origanum vulgare L | Tetracycline | S. aureus I-58 | MDM | 4-fold reduction in MIC | IEPA/E | Cirino et al., 2014 |
| Pelargonium graveolens | Gentamicin | A. baumannii, S. aureus | CBA | FICI = 0.11 | – | Rosato et al., 2007 |
| P. graveolens | Norfloxacin | S. aureus | CBA | FICI = 0.11 | – | Rosato et al., 2007 |
| Thymus broussonetii Bois | Cefixime | MDR P. aeruginosa | CBA, Cell lysis assay (CLA) | FICI = 0.5 | Disruption of bacterial membrane (DBM) | Fadli et al., 2012 |
| T. broussonetii | Cefixime | MDR S. aureus | CBA; CLA | FICI = 0.5 | DBM | Fadli et al., 2012 |
| T. broussonetii | Ciprofloxacin | MDR P. aeruginosa | CBA, CLA | FICI = 0.14 | DBM | Fadli et al., 2012 |
| T. broussonetii | Ciprofloxacin | MDR S. aureus | CBA, CLA | FICI = 0.5 | DBM | Fadli et al., 2012 |
| T. broussonetii | Gentamycin | MDR E. clocae | CBA, CLA | FICI = 0.5 | DBM | Fadli et al., 2012 |
| T. broussonetii | Gentamycin | MDR P. aeruginosa | CBA, CLA | FICI = 0.28 | DBM | Fadli et al., 2012 |
| T. broussonetii | Gentamycin | MDR S. aureus | CBA, CLA | FICI = 0.5 | DBM | Fadli et al., 2012 |
| T. broussonetii | Pristinamycin | MDR K. pneumoniae | CBA, CLA | FICI = 0.5 | DBM | Fadli et al., 2012 |
| T. broussonetii | Pristinamycin | MDR S. aureus | CBA, CLA | FICI = 0.5 | DBM | Fadli et al., 2012 |
| Thymus maroccanus Ball | Chloramphenicol | A. baumannii AP1 | MDM | 8 to 16 -fold reduction in MIC | Alteration of OM- LPS | Fadli et al., 2011 |
| T. maroccanus | Chloramphenicol | P. aeruginosa PA124 | MDM | 4 to 8 -fold reduction in MIC | IEPA/E | Fadli et al., 2011 |
| Thymus riatarum Humbert & Maire | Chloramphenicol | E. aerogenes EA27 | MDM | 16 -fold reduction in MIC | IEPA/E | Fadli et al., 2011 |
| T.riatarum | Ciprofloxacin | MDR E. clocae | CBA, CLA | FICI = 0.37 | DBM | Fadli et al., 2012 |
| T. riatarum | Ciprofloxacin | MDR K. penumoniae | CBA, CLA | FICI = 0.5 | DBM | Fadli et al., 2012 |
| T. riatarum | Ciprofloxacin | MDR P, aeruginosa | CBA, CLA | FICI = 0.15 | DBM | Fadli et al., 2012 |
| T. riatarum | Ciprofloxacin | MDR S. aureus | CBA, CLA | FICI = 0.26 | DBM | Fadli et al., 2012 |
| T. riatarum | Gentamycin | MDR E. clocae | CBA, CLA | FICI = 0.19 | DBM | Fadli et al., 2012 |
| T. riatarum | Gentamycin | MDR K. penumoniae | CBA, CLA | FICI = 0.5 | DBM | Fadli et al., 2012 |
| T. riatarum | Gentamycin | MDR K. P. aeruginosa | CBA, CLA | FICI = 0.18 | DBM | Fadli et al., 2012 |
| T. riatarum | Gentamycin | MDR S. aureus | CBA, CLA | FICI = 0.5 | DBM | Fadli et al., 2012 |
| T. riatarum | Pristinamycin | MDR E. cloacae | CBA, CLA | FICI = 0.5 | DBM | Fadli et al., 2012 |
| T. riatarum | Pristinamycin | MDR S. aureus | CBA, CLA | FICI = 0.5 | DBM | Fadli et al., 2012 |
| Zataria multiflora | Vancomycin | S. aureus | CBA | FICI = 0.32 | – | Mahboubi and Bidgoli, 2010 |
| Carvacrol | Ampicillin | S. aureus | CBA | FICI < 0.3 | – | Palaniappan and Holley, 2010 |
| Carvacrol | Bacitracin | S. aureus | CBA | FICI < 0.3 | – | Palaniappan and Holley, 2010 |
| Carvacrol | Nitrofurantoin | K. oxytoca | CBA | FICI ≤ 0.5 | – | Zhang et al., 2011 |
| Carvacrol | Ciprofloxacin | S. aureus | MDM, CLA | 8-fold reduction in MIC | DBM | Fadli et al., 2012 |
| Carvacrol | Ciprofloxacin | K. pneumoniae | MDM, CLA | 4-fold reduction in MIC | DBM | Fadli et al., 2012 |
| Carvacrol | Ciprofloxacin | E. cloacae | MDM, CLA | 4-fold reduction in MIC | DBM | Fadli et al., 2012 |
| Carvacrol | Tetracycline | S. aureus I-58 | MDM | 2-fold reduction in MIC | IEPA/E | Cirino et al., 2014 |
| Eugenol | Vancomycin, β-lactams | E. aerogenes, P. aeruginosa | MDM, CBA | – | DBM | Hemaiswarya and Doble, 2009 |
| Geraniol | Chloramphenicol | E. aerogenes EA27 | MDM | 256-fold reduction in MIC | IEPA/E | Lorenzi et al., 2009 |
| Thymol | Tetracycline | S. aureus I-58 | MDM | 2-fold reduction in MIC | IEPA/E | Cirino et al., 2014 |
CBA, checkerboard assay; CLA, cell lysis assay; IZGC, change in inhibition zone by EO gaseous contact; OM, outer membrane, LPS, lipopolysaccharide structure; IEPA/E, inhibition of efflux pumps activity/expression; DBM, disruption of bacterial membrane.