TABLE 1.
Susceptibility profiles of the parental strains and one-step selection mutants for SAM, TZP, and CZAa
| Strain | Combination for selection | Mean growth rate ± SD | SAM MICratio (mg/L) | SAM MIC (mg/L) | TZP MICratio (mg/L) | TZP MIC (mg/L) | TZ MIC (mg/L) | CZA MICratio (mg/L) | CZA MIC (mg/L) |
|---|---|---|---|---|---|---|---|---|---|
| WT | None | 1 ± 0.02 | 4 | 4 | 2 | 2 | 0.5 | 0.25 | 0.25 |
| WT/pUUH | None | 0.97 ± 0.01 | 32 | >256 | 16 | 8 | 64 | 0.25 | 0.25 |
| DA61263 | SAM | 0.84 ± 0.05 | 256 | >256 | 256 | 256 | 0.5 | 0.25 | 0.25 |
| DA61264 | 0.75 ± 0.01 | 256 | >256 | 256 | 256 | 0.5 | 0.25 | 0.25 | |
| DA61265 | 0.81 ± 0.01 | 256 | >256 | 64 | 256 | 64 | 1 | 0.5 | |
| DA61266 | 0.87 ± 0.02 | 128 | >256 | 32 | 128 | 0.5 | 0.5 | 0.25 | |
| DA61267 | 0.99 ± 0.04 | 256 | >256 | 64 | 256 | 64 | 0.5 | 0.25 | |
| DA61268 | TZP | 1.00 ± 0.02 | 64 | >256 | 128 | >256 | 64 | 1 | 0.25 |
| DA61269 | 0.98 ± 0.02 | 64 | >256 | 64 | 256 | 64 | 1 | 0.25 | |
| DA61270 | 1.05 ± 0.02 | 64 | >256 | 128 | 256 | 64 | 1 | 0.5 | |
| DA61271 | 0.97 ± 0.03 | 64 | >256 | 128 | 256 | 64 | 0.5 | 0.25 | |
| DA61272 | 0.97 ± 0.04 | 64 | >256 | 128 | 256 | 128 | 1 | 0.25 | |
| DA61259 | CZA | 0.85 ± 0.04 | 128 | >256 | 64 | 32 | 128 | 2 | 0.25 |
| DA61260 | 0.83 ± 0.05 | 64 | >256 | 32 | 128 | 64 | 4 | 0.25 | |
| DA61261 | 0.91 ± 0.04 | 32 | 128 | 8 | 4 | 8 | 4 | 0.5 | |
| DA61262 | 0.56 ± 0.16 | 128 | >256 | 64 | 128 | >256 | 2 | 0.25 | |
| DA62411 | 0.73 ± 0.01 | 128 | >256 | 64 | >256 | >256 | 4 | 0.25 | |
a
MICs for ampicillin and piperacillin were >256 mg/L for the parental strain and all mutants. Values in boldface type exceed the clinical breakpoints set by EUCAST. Clinical breakpoints are as follows: >8 mg/L for ampicillin-sulbactam (SAM), >8 mg/L for piperacillin-tazobactam (TZP), >4 mg/L for ceftazidime (TZ), and >8 mg/L for ceftazidime-avibactam (CZA). WT, wild type.