TABLE 4.
MICs of selected β-lactams and E. cloacae NmcA specific β-lactamase activities in different host strains
| Strain | Relevant genotype | MIC (μg/ml)a
|
β-Lactamase activityb
|
|||||||
|---|---|---|---|---|---|---|---|---|---|---|
| ATM | ATM-CA | CAZ | CAZ-CA | IMP | IMP-CA | Basal | Inducedc | Ratio | ||
| E. cloacae | ||||||||||
| NOR-1 | WT | 16 | 0.12 | 0.5 | 0.5 | 8 | 1 | 0.85 | 27 | 31 |
| NOR-1D3 | CAZr mutant | 128 | 128 | 32 | 32 | 16 | 2 | 55 | 175 | 3 |
| NOR-1D1→12 | CAZr mutant | 256 | 128 | 256 | 256 | 32 | 2 | 475 | 480 | 1 |
| NOR-1D1/pNH5 | CAZr mutant with E. coli ampD | 128 | 64 | 32 | 32 | 16 | 1 | 29 | 285 | 10 |
| NOR-1D1/pSM13 | CAZr mutant with ampD from NOR-1 | 64 | 32 | 8 | 8 | 8 | 1 | 4.5 | 75 | 16 |
| NOR-1D1/pSM3 | CAZr mutant with ampD from NOR-1D3 | 128 | 128 | 64 | 64 | 16 | 2 | 320 | 350 | 1 |
| NOR-1D1/pSM1→12 | CAZr mutant with ampD from NOR-1D1→12 | 256 | 128 | 256 | 256 | 32 | 1 | 470 | 465 | 1 |
| MHN2d | ΔampD/Ee | 64 | 64 | 256 | 256 | 0.5 | 0.5 | 20,000 | 19,000 | 1 |
| MHN2/pNH5d | ΔampD/E, E. coli ampD | 32 | 32 | 32 | 32 | 0.5 | 0.5 | 685 | 4,890 | 7 |
| MHN2/pSM13d | ΔampD/E, ampD from NOR-1 | 1 | 1 | 0.5 | 0.5 | 0.25 | 0.25 | 0.75 | 20 | 27 |
| MHN2/pSM1→12d | ΔampD/E, ampD from NOR-1D1→12 | 128 | 64 | 256 | 256 | 0.5 | 0.5 | 20,500 | 18,300 | 1 |
| E. coli | ||||||||||
| MC4100 | WT | 0.06 | 0.06 | 0.25 | 0.12 | 0.12 | 0.12 | NDf | ND | |
| MC4100/pPTN-3 | WT strain with nmcA and nmcR (400 copies) | 512 | 128 | 2 | 0.25 | >128 | 8 | 1,220 | 1,435 | 1 |
| MC4100/pPTN-7 | WT strain with nmcA and nmcR (20–40 copies) | 128 | 32 | 1 | 0.25 | 128 | 4 | 455 | 910 | 2 |
| MC4100/pPTN-9 | WT strain with nmcA and nmcR (1–5 copies) | 64 | 4 | 0.5 | 0.25 | 64 | 2 | 200 | 710 | 4 |
| JRG582 | ΔampD mutant | 0.06 | 0.06 | 0.03 | 0.03 | 0.12 | 0.12 | ND | ND | |
| JRG582/pPTN-3 | ΔampD mutant with nmcA and nmcR (400 copies) | >512 | 256 | 1 | 0.25 | >128 | 32 | 2,720 | 1,690 | 1 |
| JRG582/pPTN-7 | ΔampD mutant with nmcA and nmcR (20–40 copies) | >512 | 128 | 2 | 0.5 | >128 | 32 | 2,400 | 2,090 | 1 |
| JRG582/pPTN-9 | ΔampD mutant with nmcA and nmcR (1–5 copies) | 256 | 64 | 2 | 0.5 | >128 | 16 | 1,150 | 1,020 | 1 |
| JRG582/pPTN-9/pSM13 | ΔampD mutant with nmcA and nmcR and ampDNOR-1 | 64 | 16 | 0.25 | 0.12 | 8 | 1 | 9.5 | 120 | 12 |
a
Drug abbreviations: ATM, aztreonam; CAZ, ceftazidime; IPM, imipenem; CA, clavulanic acid.
b
Specific activity (in micromoles per minute per milligram of protein). Imipenem was used as a substrate, unless indicated otherwise. The β-lactamase activities are geometric mean determinations for three independent cultures. The standard deviations were within 10% for each strain.
c
Induced with cefoxitin.
d
Cephalothin was used as the substrate for the determination of the specific activities for these strains.
e
ΔampD/E, deletion of ampD or ampE.
f
ND, not determined.