TABLE 4.
β-Lactamase activity of S. maltophilia L1 and L2 β-lactamase-deficient mutants
| Strain | β-Lactamase phenotype | Assay buffera | Hydrolysis rate ofb
|
|
|---|---|---|---|---|
| Imipenem | Nitrocefin | |||
| ULA-511 | Parent (L1+ L2+) | KPi-ZnCl2 | 10.58 | 46.57 |
| KPi-Na2-EDTA | 3.27 | 24.73 | ||
| K1385 | MDR (L1+ L2+) | KPi-ZnCl2 | 12.71 | 59.04 |
| KPi-Na2-EDTA | 2.83 | 43.68 | ||
| K1445 | ULA-511 ΔL1 | KPi-ZnCl2 | 0.00 | 40.53 |
| KPi-Na2-EDTA | 0.00 | ND | ||
| K1446 | K1385 ΔL1 | KPi-ZnCl2 | 0.00 | 41.45 |
| KPi-Na2-EDTA | 0.00 | ND | ||
| K1447 | ULA-511 ΔL2 | KPi-ZnCl2 | 10.94 | 5.19 |
| KPi-Na2-EDTA | 1.72 | 0.02 | ||
| K1448 | K1385 ΔL2 | KPi-ZnCl2 | 8.14 | 4.21 |
| KPi-Na2-EDTA | 2.31 | 0.01 | ||
| K1449 | ULA-511 ΔL1 ΔL2 | KPi-ZnCl2 | 0.00 | 0.02 |
| KPi-Na2-EDTA | 0.00 | 0.04 | ||
| K1450 | K1385 ΔL1 ΔL2 | KPi-ZnCl2 | 0.00 | 0.03 |
| KPi-Na2-EDTA | 0.00 | 0.02 | ||
a
Assays were carried out in 50 mM potassium phosphate buffer (KPi), pH 7.2, in the presence of 0.1 mM ZnCl2 or 1 mM Na2-EDTA.
b
Hydrolysis rate is presented as micromoles of substrate (imipenem or nitrocefin) hydrolyzed per milligram of protein per minute. ND, not determined.