TABLE 1.
β-Lactamase activities of E. coli TOP10 strains harboring recombinant plasmids
| Recombinant E. coli strain | β-Lactamase activity (μU/mg of protein)a
|
|
|---|---|---|
| Cephalothin | Cefepime | |
| TOP10(pEC1) | 110,000 | 7 |
| TOP10(pEC2) | 110,000 | 7 |
| TOP10(pEC13) | 35,000 | 500 |
| TOP10(pEC14) | 60,000 | 200 |
| TOP10(pEC15) | 7,000 | 30 |
| TOP10(pEC16) | 110,000 | 50 |
| TOP10(pEC17) | 14,000 | 30 |
| TOP10(pEC18) | 35,000 | 500 |
| TOP10(pEC19) | 7,000 | 30 |
| TOP10(pKL) | 9,000 | 70 |
a
One unit of β-lactamase activity is defined as 1 μmol of cephalothin or cefepime hydrolyzed per min. The β-lactamase activities shown are geometric mean determinations for three independent cultures. The standard deviations were within 10%. Recombinant E. coli strains TOP10(pEC13) to TOP10(pEC19) and TOP10(pKL) produced ESAC β-lactamases, whereas TOP10(pEC1) and TOP10(pEC2) produced typical cephalosporinases.