Table 3.
The results of checkerboard analysis of drug interaction between EEP20 and different antibiotics against S. aureus ATCC 25923.
| Agent | MIC (µg/mL) | FIC | ΣFIC | Interpretation | |
|---|---|---|---|---|---|
| Alone | Combination | ||||
| EEP 20 | 128 | 16 | 0.125 | 0.375 | Synergy |
| Amikacin | 1 | 0.25 | 0.25 | ||
| EEP 20 | 128 | 32 | 0.25 | 0.5 | Synergy |
| Kanamycin | 2 | 0.5 | 0.25 | ||
| EEP 20 | 128 | 32 | 0.25 | 0.5 | Synergy |
| Gentamicin | 0.125 | 0.0312 | 0.25 | ||
| EEP 20 | 128 | 16 | 0.125 | 0.375 | Synergy |
| Tetracycline | 0.5 | 0.125 | 0.25 | ||
| EEP 20 | 128 | 16 | 0.125 | 0.625 | Indifferent * |
| Chloramphenicol | 4 | 2 | 0.5 | ||
| EEP 20 | 128 | 16 | 0.125 | 0.375 | Synergy |
| Fusidic acid | 0.5 | 0.125 | 0.25 | ||
| EEP 20 | 128 | 16 | 0.125 | 0.625 | Indifferent * |
| Erythromycin | 0.5 | 0.25 | 0.5 | ||
| EEP 20 | 128 | 16 | 0.125 | 0.625 | Indifferent * |
| Linezolid | 4 | 2 | 0.5 | ||
| EEP 20 | 128 | 128 | 1 | 2 | Indifferent |
| Levofloxacin | 0.125 | 0.125 | 1 | ||
| EEP 20 | 128 | 32 | 0.25 | 0.750 | Indifferent * |
| Norfloxacin | 0.5 | 0.25 | 0.5 | ||
| EEP 20 | 128 | 128 | 1 | 2 | Indifferent |
| Rifampicin | 0.015 | 0.015 | 1 | ||
| EEP 20 | 128 | 32 | 0.25 | 0.750 | Indifferent * |
| Mupirocin | 0.25 | 0.125 | 0.5 | ||
| EEP 20 | 128 | 64 | 0.5 | 1 | Indifferent |
| Bacitracin | 32 | 16 | 0.5 | ||
| EEP 20 | 128 | 64 | 0.5 | 0.625 | Indifferent * |
| Oxacillin | 0.25 | 0.062 | 0.125 | ||
| EEP 20 | 128 | 64 | 0.5 | 1 | Indifferent |
| Ampicillin | 0.25 | 0.125 | 0.5 | ||
| EEP 20 | 128 | 64 | 0.5 | 1 | Indifferent |
| Teicoplanin | 2 | 1 | 0.5 | ||
Indifferent *—according to the classification proposed by Odds combined therapy with these values of ΣFIC should be classified as indifferent, however, some slight decrease of MIC values of both agents (used in combination) was observed.