TABLE 3.
MICs of β-lactam antibioticsa
| Antibiotic | MIC (μg/mL) for strain: |
||||||
|---|---|---|---|---|---|---|---|
| PA14 | ΔPA4292 | ΔPA4292/pUCP24-PA4292 | phzC1::Tn | Δphz2 | ΔPA4292 phzC1::Tn | ΔPA4292 Δphz2 | |
| Aztreonam/avibactam | 4 | 8 | 4 | 2 | 4 | 4 | 4 |
| Aztreonam | 4 | 8 | 4 | 2 | 4 | 4 | 4 |
| Ceftazidime | 1 | 2 | 1 | 1 | 1 | 2 | 1 |
| Cefepime | 0.5 | 1 | 0.5 | 0.5 | 0.5 | 1 | 0.5 |
| Carbenicillin | 64 | 128 | 32 | 32 | 64 | 64 | 64 |
| Aztreonam-ceftazidime/avibactam | 2/1 | 4/2 | 2/1 | 1/0.5 | 2/1 | 2/1 | 2/1 |
a
The MIC of aztreonam-ceftazidime/avibactam is expressed as the concentrations of aztreonam/ceftazidime; avibactam was fixed at 4 μg/mL. The synergistic ratio of aztreonam to ceftazidime was assessed by checkerboard assays. Aztreonam: ceftazidime = 2:1, FICI = 0.5. Data represent results from three independent experiments.