TABLE 1.
β-Lactamase activity observed in S. maltophilia K279a and in ceftazidime-resistant K279a mutants and clinical isolates carrying different mutations
| Isolate | β-Lactamase activity (mean ± SEM) (nmol · min−1 · μg−1 protein nitrocefin hydrolyzed in cell extracts) | Relevant amino acid changes (relative to K279a) |
|---|---|---|
| K279a | 0.02 ± 0.004 | WTa |
| KM11 | 0.99 ± 0.03 | Asp135Asn in AmpR |
| KCAZ10 | 1.52 ± 0.04 | 159–168del in AmpD |
| KCAZ14 | 0.72 ± 0.01 | 140–146del in Mpl |
| 49-6147 | 0.45 ± 0.12 | 92–109del Mpl |
| 3800 | 0.73 ± 0.03 | Truncation at 368 in Mpl |
| 98 | 1.76 ± 0.07 | IS insertion in ampD, Ala85Glyb in Mpl |
| ula-511 | 1.19 ± 0.01 | Truncation at 360 in Mpl |
| KCAZ14(pBBRMCS-5) | 1.14 ± 0.10 | |
| KCAZ14(pBBRMCS-5::mpl) | 0.03 ± 0.003 |
a
WT, wild type.
b
Random genetic drift.