Table 1.

Resistance levels conferred by the parent and hybrid metallo-β-lactamasesa

Plasmidβ-LactamaseAmino acid residue at position:MIC (μg/ml) ofb:
87196LORCEFCTXCAZAMPIMPATM
pMS401IMP-3GlyGly64512646481<0.5
pMS402HybridGluGly64512646481<0.5
pMS502HybridGlySer321283264642<0.5
pMS501IMP-1GluSer321283264642<0.5
pHSG398 Δ Hd28<0.5<0.54<0.5<0.5
None28<0.5<0.54<0.5<0.5
  • a Host strain: E. coli K-12 JM83.

  • b LOR, cephaloridine; CEF, cephalothin; CTX, cefotaxime; CAZ, ceftazidime; AMP, ampicillin; IMP, imipenem; ATM, aztreonam.