Table 4.

MICs of β-lactam antibiotics and specific activities of AmpC in P. aeruginosa mutants carrying wild-typeampDE and in AmpD-defective mutant

Strain and plasmidMIC (μg/ml)β-Lactamase activitya
AmpicillinCefotaximeNoninducedInducedb
PAO1512327 ± 0.5687 ± 32
PAO1-D4,0961,024256 ± 145,560 ± 239
PAO42542,0483280 ± 33,100 ± 90
PAO4254/pUCP261,0243292 ± 52,875 ± 158
PAO4254/pHUL4DE261,0243283 ± 42,288 ± 170
Ps50SAI−con 2,0482563,780 ± 1505,900 ± 220
Ps50SAI−con/pHUL4DE261,0245122,870 ± 1923,397 ± 200
M14054,09651210,550 ± 35012,650 ± 400
M1405/pHUL4DE262,0485127,286 ± 3938,931 ± 518
M2297−con 2,0485128,200 ± 3009,330 ± 320
M2297−con/pHUL4DE261,0245126,949 ± 3246,834 ± 513
  • 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.