TABLE 5.
Susceptibilities of PAO1 and ampD null mutants to ceftazidime and aztreonam in the presence or absence of EtBuPUGa
| Strain | MICb (mg ml−1)
|
Antibiotic clearing radius (mm)c
|
||||||
|---|---|---|---|---|---|---|---|---|
| Ceftazidime
|
Aztreonam
|
Ceftazidime
|
Aztreonam
|
|||||
| −I | +I | −I | +I | −I | +I | −I | +I | |
| PAO1 | 1 | 0.5 | 1 | 0.25 | 11.4 | 13.1 | 12.5 | 15.1 |
| PAΔD | 8 | 4 | 6 | 3 | ||||
| PAΔDh2 | 0.75 | 0.19 | 1 | 0.25 | 10.1 | 12.3 | 11.8 | 14.0 |
| PAΔDh3 | 1 | 0.5 | 1.5 | 0.75 | ||||
| PAΔDDh2 | 12 | 6 | 16 | 8 | ||||
| PAΔDDh3 | 48 | 48 | 16 | 8 | ||||
| PAΔDh2Dh3 | 0.75 | 0.75 | 0.5 | 0.25 | ||||
| PAΔDDh2Dh3 | 48 | 48 | 24 | 12 | 9.2 | 9.5 | 10.7 | 11.9 |
a
The bacterial strains were treated with the NagZ selective inhibitor EtBuPUG (+I) or were not treated with EtBuPUG (−I).
b
The MIC was determined by the broth microdilution method. Measurements were performed in triplicate.
c
Sensitivity was determined by an agar diffusion assay. Filter discs (diameter, 6 mm) loaded with 30 μg of ceftazidime or aztreonam with or without the inhibitor EtBuPUG were placed onto an agar plate inoculated with the indicated strain. After incubation overnight, the radius (from the center of the disc) of the zone of clearance was measured.