Table 1.

MICs of β-lactams for P. aeruginosa RP-1,E. coli JM109 harboring recombinant plasmid pPL20, reference strain E. coli JM109, reference strain P. aeruginosa ATCC 27853, and its stably derepressed cephalosporinase-producing mutant, Mut

Antibiotic(s)MIC (μg/ml) against:
P. aeruginosa RP-1E. coli JM109 (pPL20)E. coli JM109P. aeruginosa ATCC 27853P. aeruginosa Mut
Amoxicillin>5125122>512>512
Amoxicillin + CLAa>51242>512>512
Ticarcillin>512>5122232
Ticarcillin + CLA6441232
Piperacillin2562561116
Piperacillin + CLA3221116
Cephalothin>512>5124>512>512
Cephalothin + CLA>51242>512>512
Cefoxitin>51288>512>512
Ceftazidime3280.250.258
Ceftazidime + CLA80.250.250.258
Cefotaxime>512320.062>512
Cefotaxime + CLA2560.120.062>512
Imipenem20.120.060.50.5
Aztreonam3280.120.52
Aztreonam + CLA160.120.120.52
  • a CLA, clavulanic acid at a fixed concentration of 2 μg/ml (MIC for E. coli JM109, 16 μg/ml).