TABLE 3.
β-Lactamase activity of M. morganii 1 with or without pNH5 (ampD of E. cloacae) and E. coli MC4100 harboring either recombinant plasmid pAC-1 (ampR and ampC genes) or pAC-2 (ampC gene)
| Strain | β-Lactamase activity (mU/mg of protein)a
|
|
|---|---|---|
| Basal level | Induced | |
| M. morganii 1b | 1,430 | 1,350 |
| M. morganii 1(pNH5)b | 8 | 400 |
| E. coli MC4100(pAC-1)c | 200 | 1,350 |
| E. coli MC4100(pAC-2)c | 1,160 | 1,100 |
a
One unit of β-lactamase is defined as 1 μmol of cephalothin hydrolyzed per min. The β-lactamase activities are geometric mean determinations for three independent cultures. The standard deviations were within 10%.
b
Imipenem (0.5 μg/ml) was used as the inducer.
c
Cefoxitin (4 μg/ml) was used as the inducer.