Table 1.
Etest MIC (μg/mL), Etest Synergy Method, and Time-Kill Assay.
| P. aeruginosa | ||||
| n = 31 | LVX MIC | TZP MIC | Synergy Testing (LVX + TZP) | |
|
| ||||
| Etest | TKA | |||
| Etest(a) | Etest(a) | ΣFIC(a) | Log10change(b) | |
|
| ||||
| 1 | > 32 | > 256 | 2.0 I | −1.4 I |
| 2 | 8 | > 256 | 0.4 S | −3 S |
| 3 | 32 | > 256 | 0.4 S | 0 I* |
| 4 | > 32 | > 256 | 2.0 I | −2 S* |
| 5 | > 32 | 4 | 1.2 I | −0.7 I |
| 6 | > 32 | 16 | 0.5 S | −3.4 S |
| 7 | > 32 | 4 | 1.0 I | −2 S* |
| 8 | > 32 | > 64 | 2.0 I | +1.3 I |
| 9 | 32 | > 4 | 0.004 S | −2.4 S |
| 10 | > 32 | > 4 | 0.8 I | +1.4 I |
| 11 | > 32 | > 256 | 1.5 I | +1.3 I |
| 12 | > 32 | > 256 | 2.0 I | −1.5 I |
| 13 | > 32 | > 256 | 1.2 I | −0.7 I |
| 14 | > 32 | > 256 | 2.0 I | −0.4 I |
| 15 | > 32 | > 256 | 2.0 I | −1 I |
| 16 | > 32 | > 256 | 0.2 S | −2 S |
| 17 | > 32 | 16 | 1.4 I | −0.4 I |
| 18 | > 32 | > 256 | 2.0 I | −0.6 I |
| 19 | > 32 | > 256 | 1.3 I | −1.1 I |
| 20 | > 32 | > 256 | 2.0 I | −3.2 S* |
| 21 | > 32 | 32 | 0.9 I | −4S* |
| 22 | > 32 | > 256 | 2.0 I | −0.1 I |
| 23 | > 32 | 32 | 0.5 S | −2 S |
| 24 | > 32 | 16 | 1.1 I | −0.4 I |
| 25 | > 32 | > 256 | 0.6 I | −1.3 I |
| 26 | > 32 | 32 | 0.8 I | −3.8 S* |
| 27 | > 32 | > 256 | 0.5 S | −2 S |
| 28 | > 32 | 8 | 1.0 I | −3.3 S* |
| 29 | > 32 | > 256 | 1.1 I | −1.1 I |
| 30 | > 32 | > 256 | 0.3 S | −2.1 S |
| 31 | > 32 | > 256 | 0.3 S | −2.8 S |
*Pseudomonas aeruginosa strains with discordant synergy results. (a)Performed in triplicate. (b)Values represent the log10 change in CFU/mL in the time-kill assay after 24 hour exposure to the combination of levofloxacin (LVX) and piperacillin/tazobactam (TZP) compared to the most active drug alone. Negative values indicate a decrease in colony count; positive values indicate an increase in colony count. S: synergy; I: indifference.