TABLE 2.
Combination Indices for Farnesol-Antibiotic Combinations
| Ratios | CI values in mean (SD) | Ratios | CI values in mean (SD) | ||
|---|---|---|---|---|---|
| FSL: NAF | CED75 | CED90 | FSL:VAN | CED75 | CED90 |
| ATCC 55133 | |||||
| ED50 1:1 | 0 (0) | 0.26 (0.45) | ED50 1:1 = ED90 1:1 | 0.13 (0.11) | 0.1 (0.02) |
| ED90 1:1 | 0.5 (0.5) | 0.04 (0.01) | ED90 1:2 | 0.10 (0.07) | 0.07 (0.02) |
| ED90 1:2 | 0.13 (0.11) | 0.06 (0.01) | ED90 2:1 | 0.18 (0.17) | 0.1 (0.04) |
| ED90 2:1 | 0.22 (0.19) | 0.07 (0.03) | |||
| 1457 | |||||
| ED75 1:1 | 3.82 (0.53) | 0.05 (0) | ED50 1:1 = ED75 1:1 | 0.24 (0.05) | 0.08 (0.02) |
| ED75 1:2 | 2.41 (1.80) | 0.21 (0.13) | ED75 1:2 | 0.29 (0.09) | 0.15 (0.03) |
| ED75 1:4 | 0.46 (0.53) | 0.34 (0.13) | ED75 2:1 | 0.21 (0.03) | 0.07 (0.04) |
| 1457 agr- | |||||
| ED75 1:1 | 0.69 (0.26) | 0.41 (0.35) | ED50 1:1 = ED75 1:1 | 0.30 (0.29) | 0.2 (0.11) |
| ED75 1:2 | 0.55 (0.51) | 0.59 (0.13) | ED75 1:2 | 0.33 (0.28) | 0.35 (0.16) |
| ED75 1:4 | 0.48 (0.42) | 0.9 (0.79) | ED75 2:1 | 0.26 (0.25) | 0.14 (0.06) |
| 1457luxS- | |||||
| ED75 1:1 | 0.21 (0.30) | 0.03 (0.02) | ED50 1:1 = ED75 1:1 | 0.27 (0.06) | 0.05 (0.02) |
| ED75 1:2 | 0.01 (0.02) | 0.09 (0.07) | ED75 1:2 | 0.28 (0.06) | 0.06 (0.024) |
| ED75 1:4 | 0.08 (0.07) | 0.12 (0.09) | ED75 2:1 | 0.25 (0.1) | 0.05 (0.02) |
| ED50 1:1 | 0.29 (0.27) | 10.57 (182) | ED50 1:1 | 0.10 (0.03) | 0.03 (0.014) |
FSL- farnesol, NAF-nafcillin, VAN-vancomycin. ED50, ED75, and ED90 represent 50%, 75% and 90% inhibitory effects of the individual antimicrobial agent respectively. CED75 and CED90 represent 75% and 90% inhibitory effects of farnesol-antibiotic combination respectively. Combination indices (CI) derived by the median effects principle, indicate synergy if CI < 1, additive effect if CI=1 and antagonism if CI > 1. Non synergistic combinations are italicized and bolded.