Table 1.

Antibiotic susceptibilities of various P. aeruginosa strains that are deficient in or that overexpress themexZ and mexXY genes

Strain (plasmid)MIC (μg ml−1)a
AknGmTmIspNetTetEryCipNor
PAO1210.521162560.030.125
PAO1(pJR120)10.50.540.5322560.060.125
PAO1(pAGH97)1682816645120.52
11Bb 0.50.1250.1250.50.1254320.030.125
11B(pJR120)10.50.510.5161280.060.125
11B(pAGH97)16821616645120.52
PAO1Tc 0.50.1250.1250.250.06264 NDd ND
PAO1T(pAGH97)0.50.250.250.50.125264NDND
PAO1T(pAGH97; pOMI5)8818832512NDND
  • a 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.

  • b 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.

  • c No modification of MICs was observed for strain PAO1T transformed with pJR120.

  • d ND, not determined.