TABLE 1.

MICs of β-lactams for K. pneumoniae GR, its E. coli transconjugant TcGR, and an E. coli recipient strain

β-Lactam(s)aMIC (μg/ml)
K. pneumoniae GRE. coli J53 TcGRE. coli J53
Amoxicillin>256>2564
Amoxicillin + CLA48244
Ticarcillin>256>2562
Ticarcillin + CLA>256>2562
Piperacillin>2561281
Piperacillin + TZB>2561281
Cephalothin>256>2564
Cefoxitin6442
Cefotaxime>3240.06
Cefotaxime + CLA320.380.06
Ceftazidime>25640.06
Ceftazidime + CLA9610.12
Aztreonam>256160.03
Aztreonam + CLA>2561.50.03
Cefepime>2561.50.03
Imipenem121.50.12
Imipenem + CLA0.750.250.12
Meropenem60.380.03
Meropenem + CLA30.0940.03
Ertapenem120.380.03
Ertapenem + CLA60.0940.03
Tigecycline30.50.5
Gentamicin1.50.0640.064
Colistin1280.380.38
  • a CLA, clavulanic acid at a fixed concentration of 2 μg/ml; TZB, tazobactam at fixed concentration of 4 μg/ml.