Table 2.
Effect of combined colistin and meropenem against Pseudomonas aeruginosa isolates (n=25)
| Isolate number | MIC of colistin alone µg/ml | MIC of meropenem alone µg/ml | MIC of colistin with meropenem µg/ml | MIC of meropenem with colistin µg/ml | FIC | Interpretation |
|---|---|---|---|---|---|---|
| P1 | 2 | 64 | 1 | 128 | 2.5 | Indifference |
| P2 | 4 | 64 | 1 | 2 | 0.28 | Synergy |
| P3 | 2 | 64 | 1 | 64 | 1.5 | Additive |
| P4 | 16 | 64 | 0.5 | 1 | 0.26 | Synergy |
| P5 | 0.5 | 4 | 8 | 0.25 | 2.5 | Indifference |
| P6 | 0.5 | 64 | 0.25 | 0.5 | 0.26 | Synergy |
| P7 | 0.5 | 64 | 1 | 64 | 3 | Indifference |
| P8 | 0.5 | 32 | 0.5 | 32 | 2 | Additive |
| P9 | 0.5 | 128 | 0.25 | 32 | 0.75 | Additive |
| P10 | 4 | 16 | 2 | 8 | 1 | Additive |
| P11 | 16 | 8 | 8 | 4 | 1 | Additive |
| P12 | 0.5 | 128 | 0.25 | 32 | 0.75 | Additive |
| P13 | 1 | 16 | 0.5 | 8 | 1 | Additive |
| P14 | 0.5 | 32 | 0.5 | 32 | 2 | Additive |
| P15 | 0.25 | 32 | 0.125 | 8 | 0.75 | Additive |
| P16 | 2 | 256 | 0.5 | 128 | 0.75 | Additive |
| P17 | 1 | 16 | 1 | 16 | 2 | Additive |
| P18 | 0.125 | 16 | 0.0625 | 16 | 3 | Indifference |
| P19 | 1 | 32 | 1 | 32 | 2 | Additive |
| P20 | 0.125 | 16 | 0.0625 | 8 | 1 | Additive |
| P21 | 2 | 32 | 0.5 | 16 | 0.75 | Additive |
| P22 | 1 | 64 | 0.5 | 2 | 0.53 | Additive |
| P23 | 1 | 4 | 0.25 | 0.5 | 0.37 | Synergy |
| P24 | 8 | 8 | 0.125 | 0.5 | 0.26 | Synergy |
| P25 | 0.5 | 64 | 0.125 | 4 | 0.31 | Synergy |
MIC=Minimum inhibitory concentration, FIC=Fractional inhibitory concentration