Table 2.
β-Lactamase activities of S. maltophilia KJ and its derived strains
| S. maltophilia strain | β-Lactamase sp act (Una/mg) |
|
|---|---|---|
| Basal | Inducedb | |
| (A) KJ | 10 ± 1.8 | 1,628 ± 197 |
| KJΔZ | 7 ± 1.0 | 390 ± 51 |
| KJΔL1 | 5 ± 0.9 | 585 ± 65c |
| KJΔL1ΔZ | 15 ± 2.1 | 152 ± 20c |
| KJΔL2 | 9 ± 1.3 | 114 ± 18d |
| KJΔL2ΔZ | 5 ± 1.0 | 26 ± 3.2d |
| KJΔDI | 4,448 ± 752 | 4,592 ± 560 |
| KJΔDIΔZ | 88 ± 10 | 551 ± 62 |
| KJΔmrcA | 1,012 ± 190 | 2,496 ± 275 |
| KJΔmrcAΔZ | 981 ± 102 | 1,509 ± 182 |
| KJΔDIΔmrcA | 4,751 ± 876 | 5,940 ± 823 |
| KJΔDIΔmrcAΔZ | 955 ± 101 | 1,824 ± 204 |
| KJ(pRK415) | 9 ± 2.1 | 1,329 ± 150 |
| KJ(pRK-Z) | 8 ± 1.1 | 1,365 ± 143 |
| KJΔZ(pRK415) | 12 ± 1.3 | 402 ± 52 |
| KJΔZ(pRK-Z) | 10 ± 1.5 | 1,254 ± 142 |
| KJΔmrcA(pRK415) | 924 ± 112 | 2,135 ± 272 |
| KJΔmrcA(pRKDI) | 52 ± 10 | 789 ± 98 |
a
One unit of β-lactamase activity is defined as 1 nanomole of nitrocefin hydrolyzed per minute. The results are expressed as the mean ± standard deviation of three independent determinations.
b
Twenty micrograms per milliliter cefuroxime as the inducer, except for strains KJΔL1, KJΔL1ΔZ, KJΔL2, and KJΔL2ΔZ.
c
Twenty micrograms per milliliter cefoxitin as the inducer.
d
Twenty micrograms per milliliter aztreonam as the inducer.