TABLE 3.
Relative activities and 50% inhibitory concentrations determined with β-lactamase extracts of cultures of E. coli DH10B harboring recombinant plasmids pPG13 (OXA-32) and pPG14 (OXA-2)
| Substrate | Relative activitya
|
IC50 (μM)
|
||
|---|---|---|---|---|
| OXA-32 | OXA-2 | OXA-32 | OXA-2 | |
| Benzylpenicillin | 100 | 100 | ||
| Ticarcillin | <1 | 6 | ||
| Piperacillin | 86 | <1 | ||
| Cephalothin | 330 | 35 | ||
| Ceftazidime | 95 | 2 | ||
| Cefotaxime | <1 | <1 | ||
| Cloxacillin | 12 | 6 | ||
| Clavulanate | 8 | 3 | ||
| Tazobactam | 0.05 | 0.05 | ||
| Imipenem | 0.01 | 0.1 | ||
| Cefoxitin | 0.01 | 0.5 | ||
a
Specific activities were determined relative to those of benzylpenicillin, which were set at 100 for each enzyme. Standard deviations were within 15% (means of three independent determinations).