TABLE 3.
Microdilution MICs for 15 strains tested by time-kill analysisa
| Strain | MIC (μg/ml)
|
||||||
|---|---|---|---|---|---|---|---|
| Piperacillin | Piperacillin-tazobactamb | Ticarcillin | Ticarcillin-clavulanate | Ampicillin | Vancomycin | Teicoplanin | |
| 1 | 4.0 | 4.0 | 64.0 | 64.0 | 2.0 | 1.0 | 0.5 |
| 2 | 8.0 | 8.0 | 256.0 | 256.0 | 4.0 | 1.0 | 1.0 |
| 3 | 1.0 | 1.0 | 16.0 | 16.0 | 1.0 | 2.0 | 0.5 |
| 4 | 64.0c | 4.0 | 256.0 | 64.0 | 32.0c | 2.0 | 2.0 |
| 5 | 8.0 | 8.0 | 256.0 | 256.0 | 4.0 | 1.0 | 1.0 |
| 6 | 2.0 | 2.0 | 32.0 | 32.0 | 2.0 | 2.0 | 0.25 |
| 7 | 4.0 | 4.0 | 32.0 | 32.0 | 2.0 | 4.0 | 0.25 |
| 8 | 4.0 | 4.0 | 32.0 | 32.0 | 1.0 | 4.0 | 1.0 |
| 9 | 2.0 | 2.0 | 32.0 | 32.0 | 2.0 | 1.0 | 0.5 |
| 10 | 64.0 | 32.0 | 256.0 | 256.0 | 8.0 | 4.0 | 0.5 |
| 11 | 64.0 | 32.0 | 128.0 | 128.0 | 8.0 | 2.0 | 1.0 |
| 12 | 4.0 | 4.0 | 64.0 | 64.0 | 2.0 | 1.0 | 0.5 |
| 13 | 4.0 | 4.0 | 64.0 | 64.0 | 2.0 | 2.0 | 0.5 |
| 14 | 8.0 | 4.0 | 128.0 | 128.0 | 4.0 | 2.0 | 1.0 |
| 15 | 8.0d | 8.0 | 128.0 | 128.0 | 2.0d | 1.0 | 1.0 |
a
An inoculum of 5 × 105 CFU/ml was used for all strains except strain 4 (β-lactamase positive) where an inoculum of 107 CFU/ml was used.
b
Tazobactam:piperacillin at a 1:8 ratio.
c
Addition of tazobactam to piperacillin at 4.0 μg/ml and of sulbactam to ampicillin lowered β-lactam MICs to 4.0 and 2.0 μg/ml, respectively.
d
Addition of tazobactam to piperacillin at 4.0 μg/ml and of sulbactam to ampicillin did not change β-lactam MICs.