TABLE 1.
Antibiotic susceptibilities of various P. aeruginosa strains that are deficient in or that overexpress the mexZ and mexXY genes
| Strain (plasmid) | MIC (μg ml−1)a
|
||||||||
|---|---|---|---|---|---|---|---|---|---|
| Akn | Gm | Tm | Isp | Net | Tet | Ery | Cip | Nor | |
| PAO1 | 2 | 1 | 0.5 | 2 | 1 | 16 | 256 | 0.03 | 0.125 |
| PAO1(pJR120) | 1 | 0.5 | 0.5 | 4 | 0.5 | 32 | 256 | 0.06 | 0.125 |
| PAO1(pAGH97) | 16 | 8 | 2 | 8 | 16 | 64 | 512 | 0.5 | 2 |
| 11Bb | 0.5 | 0.125 | 0.125 | 0.5 | 0.125 | 4 | 32 | 0.03 | 0.125 |
| 11B(pJR120) | 1 | 0.5 | 0.5 | 1 | 0.5 | 16 | 128 | 0.06 | 0.125 |
| 11B(pAGH97) | 16 | 8 | 2 | 16 | 16 | 64 | 512 | 0.5 | 2 |
| PAO1Tc | 0.5 | 0.125 | 0.125 | 0.25 | 0.06 | 2 | 64 | NDd | ND |
| PAO1T(pAGH97) | 0.5 | 0.25 | 0.25 | 0.5 | 0.125 | 2 | 64 | ND | ND |
| PAO1T(pAGH97; pOMI5) | 8 | 8 | 1 | 8 | 8 | 32 | 512 | ND | ND |
To maintain plasmids pJR120, pAGH97, or plasmid pOMI5 in transformed cells of P. aeruginosa, 50 μg of ticarcillin ml−1 or 50 μg of chloramphenicol ml−1 was added to the growth medium. No modification of MICs was observed for strain PAO1, 11B, or PAO1T when the strain was transformed with a control plasmid. Akn, amikacin; Gm, gentamicin; Tm, tobramycin; Isp, isepamicin; Net, netilmicin; Tet, tetracycline; Ery, erythromycin; Cip, ciprofloxacin; Nor, norfloxacin.
Mutant 11B was also more susceptible than wild-type strain PAO1 to fortimicin and apramycin by the disk method with the Aminoglycoside Resistance Test Kit from Schering Plough Research Institute.
No modification of MICs was observed for strain PAO1T transformed with pJR120.
ND, not determined.