Table 3.
Synergy between brevicidine and antibiotics against a clinically isolated carbapenem-resistant A. baumannii stain.
| Antibiotic | MICa at brevicidine concentrationsa of | MMD | FICI | |||
|---|---|---|---|---|---|---|
| 0 | 0.5 | 1 | 2 | |||
| Tetracyclines | ||||||
| Tetracycline | 4 | 4 | 2 | 1 | 4x | 0.5 |
| Aminoglycosides | ||||||
| Amikacin | 8 | 8 | 4 | 2 | 4x | 0.5 |
| Macrolides | ||||||
| Erythromycin | 16 | 0.5 | 0.25 | 0.13 | 128x | 0.14 |
| Azithromycin | 128 | 8 | 4 | 2 | 64x | 0.16 |
| Rifamycins | ||||||
| Rifampicin | 0.5 | 0.02 | 0.01 | 0.01 | 64x | 0.14 |
| Lipid II targeting peptide antibiotics | ||||||
| Vancomycin | 32 | 16 | 4 | 0.5 | 64x | 0.25 |
| Nisin | 4 | 1 | 0.5 | 0.5 | 8x | 0.25 |
| β-Lactams | ||||||
| Penicillin G | 256 | 256 | 256 | 128 | 2x | 0.75 |
| Ampicillin | 256 | 256 | 256 | 256 | 0 | 1.06 |
| Meropenem | 16 | 2 | 2 | 0.5 | 32x | 0.19 |
| Polymyxins | ||||||
| Polymyxin B | 1 | 1 | 1 | 1 | 0 | 1.25 |
MIC, minimum inhibitory concentration; MMD, maximum MIC decrease; FICI, fractional inhibitory concentration index [FICI = (MIC brevicidine in combination with antibiotic/MIC brevicidine) + (MIC antibiotic in combination with brevicidine/MIC antibiotic)].
aall values reported in μM. The MIC value of brevicidine against the tested clinically isolated carbapenem-resistant A. baumannii stain was 8 μM.