Table 2.

MICs of β-lactam antibiotics and specific activities of AmpC in P. aeruginosa and its mutant strains

P. aeruginosa strainβ-Lactamase inducibilityDerivationReference(s)MIC (μg/ml)β-Lactamase activitya
AmpicillinCefotaximeNoninducedInducedb
PAO1Low basal level, inducibleWild type512327 ± 0.5687 ± 32
PAO4254 (blaK)Moderate basal level, hyperinducibleLaboratory 29 2,0483280 ± 33,100 ± 96
Ps50SAI+ Low basal level, inducibleClinical isolate 5,23 256326 ± 0.41,300 ± 90
Ps50SAI−con High basal level, stably derepressedSpontaneous mutant of Ps50SAI 14,23 2,0485123,780 ± 1505,900 ± 220
M1405High basal level, stably derepressedClinical isolate 22,23 4,09651210,550 ± 35012,650 ± 400
M2297PLow basal level, induciblePretherapy clinical isolate 23 512166 ± 0.21,840 ± 80
M2297−con High basal level, stably derepressedPosttherapy clinical isolate 23 2,0485128,200 ± 3009,330 ± 320
  • a Nanomoles of nitrocefin hydrolyzed per minute per milligram of protein.

  • b Induction was carried out with 50 μg of cefoxitin/ml for 2 h.