Table 2.

MICs of β-lactams for K. pneumoniae ORI-1,E. coli DH10B harboring either natural plasmid pTK1 or recombinant plasmid pC1, and reference strain E. coli DH10B

β-Lactam(s)aMIC (μg/ml) for:
K. pneumoniae ORI-1bE. coli DH10B (pTK1)cE. coli DH10B (pC1)cE. coli DH10B
Amoxicillin>512>512>5124
Amoxicillin + CLA6464>1284
Ticarcillin>512256>5124
Ticarcillin + CLA648644
Ticarcillin + TZB>51282562
Ticarcillin + IPM>512322564
Ticarcillin + SUL>51285124
Piperacillin51216641
Piperacillin + CLA128281
Piperacillin + TZB64281
Cephalothin64322562
Cefuroxime32322562
Cefoxitin4881
Ceftazidime481280.5
Ceftazidime + CLA0.5180.5
Ceftazidime + TZB0.50.580.5
Ceftazidime + IPM10.5160.5
Ceftazidime + SUL10.5160.5
Cefotaxime0.50.540.06
Cefotaxime + CLA0.060.060.50.06
Cefotaxime + TZB0.060.0620.06
Cefotaxime + IPM0.060.1210.06
Cefotaxime + SUL0.120.0620.12
Cefepime0.250.250.50.03
Cefepime + CLA0.060.060.060.03
Cefepime + TZB0.120.060.120.03
Aztreonam0.120.2510.12
Aztreonam + CLA<0.030.120.250.12
Aztreonam + TZB0.060.50.50.12
Moxalactam0.060.060.120.06
Imipenem0.120.250.250.12
  • a CLA, clavulanic acid at a fixed concentration of 2 μg/ml; TZB, tazobactam at a fixed concentration of 2 μg/ml; IPM, imipenem at a fixed concentration of 0.01 μg/ml; SUL, sulbactam at a fixed concentration of 4 μg/ml.

  • b K. pneumoniae ORI-1 produced a SHV-1-like penicillinase, an unidentified restricted-spectrum β-lactamase, and GES-1 β-lactamase.

  • c E. coli DH10B harboring either natural plasmid pTK1 or recombinant multicopy plasmid pC1 produced GES-1 β-lactamase.