TABLE 1.
Phenotypic characterization of clinical isolates, transconjugants, and transformants producing the CMY-2 or CMY-33 plasmid-mediated AmpC β-lactamases
| Antibiotic | MIC (μg/ml) for E. colia: |
||||||
|---|---|---|---|---|---|---|---|
| Ec-1 isolate from wound (blaCMY-2) | Ec-2 isolate from BAL fluid (blaCMY-33) | NEB5α with IncI1 plasmid of Ec-1 (blaCMY-2) | NEB5α with IncI1 plasmid of Ec-2 (blaCMY-33) | DH10B pBC SK(−)/blaCMY-2b | DH10B pBC SK(−)/blaCMY-33b | DH10Bb | |
| Ampicillin | ≥32, R | ≥32, R | ≥32, R | ≥32, R | ≥512 | 128 | 4 |
| Ampicillin-sulbactam | NT | NT | NT | NT | 32 | 0.125 | 4 |
| Piperacillin | NT | NT | NT | NT | ≥512 | 32 | 2 |
| Piperacillin-tazobactam | ≤2, S | 8, S | ≤2, S | 16, S | 4 | 8 | 2 |
| Ticarcillin-clavulanate | ≤8, S | ≥256, R | ≤8, S | ≥256, R | NT | NT | NT |
| Cephalothin | ≥32, NA | ≥32, NA | ≥32, NA | ≥32, NA | ≥512 | 128 | 4 |
| Cefoxitin | 64, NA | 32, NA | 64, NA | ≥128, NA | 64 | 16 | 4 |
| Ceftriaxone | 8, R | 128, R | 16, R | ≥256, R | NT | NT | NT |
| Cefotaxime | 4, R | 64, R | 16, R | 64, R | 8 | 16 | ≤0.06 |
| Cefotaxime-clavulanate | 4, NA | 32, NA | 8, NA | 32, NA | NT | NT | |
| Ceftazidime | 8, R | ≥256, R | 32, R | ≥256, R | 256 | ≥512 | ≤0.06 |
| Ceftazidime-clavulanate | 4, NA | ≥256, NA | 16, NA | ≥256, NA | NT | NT | NT |
| Cefpodoxime | ≥64, R | ≥64, R | ≥64, R | ≥64, R | NT | NT | NT |
| Cefepime | ≤0.5, S (0.125/≤0.016) | 16, R (16/1) | ≤0.5, S | ≥32, R | 0.25 | 8 | ≤0.06 |
| Aztreonam | 4, I | ≥32, R | 8, I | ≥32, R | 8 | 16 | ≤0.06 |
| Imipenem | ≤0.25, S | ≤0.25, S | ≤0.25, S | ≤0.25, S | ≤0.5 | ≤0.5 | ≤0.5 |
| Meropenem | ≤0.5, S | ≤0.5, S | ≤0.5, S | ≤0.5, S | ≤0.06 | ≤0.06 | ≤0.06 |
| Ertapenem | ≤0.125, S | ≤0.125, S | ≤0.125, S | ≤0.125, S | NT | NT | NT |
| Gentamicin | ≤0.5, S | ≤0.5, S | ≤0.5, S | ≤0.5, S | NT | NT | NT |
| Tobramycin | ≤0.5, S | ≤0.5, S | ≤0.5, S | ≤0.5, S | NT | NT | NT |
| Amikacin | ≤2, S | ≤2, S | ≤2, S | ≤2, S | NT | NT | NT |
| Ciprofloxacin | ≤0.125, S | ≤0.125, S | ≤0.125, S | ≤0.125, S | NT | NT | NT |
| Doxycycline | ≤1, NA | ≤1, NA | ≤1, NA | ≤1, NA | NT | NT | NT |
| Tigecycline | ≤0.125, S | ≤0.125, S | ≤0.125, S | ≤0.125, S | NT | NT | NT |
| Co-trimoxazole | ≤0.25, S | ≤0.25, S | ≤0.25, S | ≤0.25, S | NT | NT | NT |
| Colistin | ≤0.125, S | ≤0.125, S | ≤0.125, S | ≤0.125, S | NT | NT | NT |
a
BAL, bronchoalveolar lavage; R, resistant; NT, not tested; S, susceptible; NA, not available; I, intermediate. The MICs were obtained with microdilution Trek panels and interpreted according to the EUCAST criteria (23). The tests were repeated three times. Values in parentheses indicate MICs obtained with the Etest method on plates without/with cloxacillin (200 μg/ml).
b
MICs for E. coli DH10B transformants containing pBC SK(−) were achieved with the agar dilution method. Consistent results were also previously obtained with the Etest method (18).