TABLE 2.
Effects of the overexpression of the three β-lactamases TEM-1, OXA-1, and CTX-M-15 on different β-lactam/β-lactamase inhibitor combinationsa
| Plasmid | AMP MIC (mg/L) | SAM MICratio (mg/L) | SAM MIC (mg/L) | PIP MIC (mg/L) | TZP MICratio (mg/L) | TZP MIC (mg/L) | TZ MIC (mg/L) | CZA MICratio (mg/L) | CZA MIC (mg/L) |
|---|---|---|---|---|---|---|---|---|---|
| Empty pBAD18 | 4 | 4 | 2 | 2 | 2 | 2 | 0.25 | 0.25 | 0.125 |
| pBAD-blaTEM-1 | >256 | 256 | >256 | >256 | 64 | 8 | 2 | 1 | 0.25 |
| pBAD-blaCTX-M-15 | >256 | 32 | 64 | >256 | 16 | 4 | 256 | 0.5 | 0.25 |
| pBAD-blaOXA-1 | >256 | 64 | 128 | >256 | 128 | 32 | 0.25 | 0.25 | 0.125 |
a
AMP, ampicillin; SAM, ampicillin-sulbactam; PIP, piperacillin; TZP, piperacillin-tazobactam; TZ, ceftazidime; CZA, ceftazidime-avibactam. Values in boldface type exceed the clinical breakpoints set by EUCAST.