TABLE 1.
MICs of β-lactams for A. fermentans RYC-MR95, E. coli harboring recombinant plasmids which produce β-lactamase ACI-1, and reference strainsa
| Antibiotic | MIC (μg/ml)
|
|||||
|---|---|---|---|---|---|---|
| RYC-MR95 | RYC4093 | RYC4356 | RYC1000/(pJC10) | RYC1000/(pJC4) | RYC1000 | |
| Penicillin | 128 | ≤0.5 | ≤0.5 | |||
| Amoxicillin | 64 | 1 | ≤0.5 | 1,024 | 8 | 8 |
| Amoxicillin-Cla | ≤0.03 | ≤0.03 | ≤0.03 | 8 | 4 | 4 |
| Ticarcillin | 256 | 1 | ≤0.5 | ≥1,024 | 4 | 4 |
| Ticarcillin-Cla | 0.25 | 0.5 | ≤0.03 | 16 | 4 | 4 |
| Cephalothin | 4 | ≤0.5 | ≤0.5 | 16 | 2 | 2 |
| Cephalothin-Cla | 2 | 0.5 | 0.25 | 4 | 2 | 2 |
| Ceftazidime | 32 | 2 | 2 | 16 | 0.12 | 0.12 |
| Ceftazidime-Cla | 2 | 2 | 0.5 | 0.5 | 0.12 | 0.12 |
| Cefotaxime | 64 | 0.5 | 0.5 | 4 | 0.03 | 0.03 |
| Cefotaxime-Cla | 0.25 | 0.5 | 0.25 | 0.03 | 0.03 | 0.03 |
| Cefepime | 1 | 0.015 | 0.03 | |||
| Cefepime-Cla | 0.015 | 0.03 | ||||
| Cefoxitin | 4 | 1 | 1 | 1 | 0.5 | 0.5 |
| Imipenem | 0.5 | 0.5 | 0.5 | 0.12 | 0.06 | 0.06 |
a
RYC-MR95 is wild-type A. fermentans producing ACI-1. RYC4093 and RYC4356 are β-lactam-susceptible A. fermentans strains. RYC1000 harboring recombinant plasmid pJC10 produced the ACI-1 β-lactamase. RYC1000 harboring recombinant plasmid pJC4 contained a truncated aci1 gene. Cla, clavulanic acid at a fixed concentration of 2 μg/ml.