TABLE 1.
MICs of β-lactams and combinations of β-lactams with commercially available β-lactamase inhibitors and penems 1 and 2
| Drug or combinationa | MIC (mg/liter) for: |
||
|---|---|---|---|
| K. pneumoniae 1534 blaKPC-2 | E. coli DH10B (pBR322) blaKPC-2 | E. coli DH10B | |
| Ampicillin | 8,192 | 4,096 | 1 |
| Ampicillin-clavulanic acid | 50/32 | 50/32 | 50/1 |
| Ampicillin-sulbactam | 50/512 | 50/512 | 50/1 |
| Piperacillin | 1,024 | 1,024 | 2 |
| Piperacillin-tazobactam | 512/64 | 512/64 | 4/0.5 |
| Piperacillin-penem 1 | 16/4 | 32/4 | 1/4 |
| Piperacillin-penem 2 | 32/4 | 64/4 | 4/4 |
| Cefotaxime | 16 | 8 | 0.06 |
| Cefotaxime-penem 1 | 0.25/4 | 0.25/4 | 0.06/4 |
| Cefotaxime-penem 2 | 0.25/4 | 0.5/4 | 0.06/4 |
| Imipenem | 8 | 8 | 0.125 |
| Imipenem-penem 1 | 2/4 | 2/4 | 0.125/4 |
| Imipenem-penem 2 | 2/4 | 2/4 | 0.25/4 |
a
In drug combinations, ampicillin was maintained at a constant concentration of 50 mg/liter and clavulanic acid and sulbactam concentrations were increased. For piperacillin-tazobactam, the two components were increased but maintained at a ratio of 8:1. Penem 1 and penem 2 were held at a constant concentration of 4 mg/liter while the concentrations of piperacillin, imipenem, and cefotaxime were increased.