Table 1.
MICs of β-lactams for E. coli MEV, the E. coli TOP10(pMEV) and TOP10(pAmpC-A) recombinant clones, and the E. coli TOP10 recipient strain
| β-Lactam | E. coli MEVa | E. coli MEVa + CLOXAc | E. coli MEVa + PAβNd | E. coli TOP10(pMEV)a | E. coli TOP10(pAmpC-A)a | E. coli TOP10 |
|---|---|---|---|---|---|---|
| Amoxicillin | >512 | 16 | >512 | >512 | 512 | 2 |
| Amoxicillin-CLAb | 512 | 8 | 512 | 512 | 512 | 2 |
| Ticarcillin | 256 | 4 | 128 | 256 | 8 | 1 |
| Ticarcillin-CLAb | 128 | 4 | 64 | 128 | 8 | 1 |
| Piperacillin | 256 | 4 | 128 | 256 | 8 | 1 |
| Piperacillin-TZBe | 128 | 4 | 64 | 64 | 8 | 1 |
| Cefotaxime | 64 | 0.5 | 16 | 32 | 1 | 0.06 |
| Ceftazidime | 256 | 1 | 128 | 256 | 2 | 0.06 |
| Cefepime | 16 | 0.5 | 2 | 2 | 0.06 | 0.06 |
| Imipenem | 0.5 | 0.25 | 0.5 | 0.25 | 0.06 | 0.06 |
| Ertapenem | 1 | 0.06 | 0.5 | 0.125 | 0.016 | 0.008 |
| Meropenem | 0.25 | 0.125 | 0.25 | 0.032 | 0.032 | 0.032 |
a
E. coli MEV and TOP10(pMEV) produced the extended-spectrum AmpC-MEV β-lactamase, E. coli TOP10(pAmpC-A) produced the narrow-spectrum AmpC-A β-lactamase, and the E. coli TOP10 recipient strain did not produce a β-lactamase.
b
CLA, clavulanic acid at 2 μg/ml.
c
Cloxacillin (CLOXA) MICs were obtained using 250 μg/ml cloxacillin-containing Mueller-Hinton agar plates.
d
PAβN was used at 26.3 μg/ml (5).
e
TZB, tazobactam at 4 μg/ml.