TABLE 4.

Etest MICs of β-lactam antibiotics against E. coli DH5α clones producing GES variants under isogenic conditions

InhibitorMIC (μg/ml)
E. coli (GES-1 [E104, G170])E. coli (GES-7 [K104, G170])E. coli (GES-2 [E104, N170])E. coli (GES-5 [E104, S170])E. coli (GES-6 [K104, S170])E. coli (GES-13 [K104, N170])E. coli DH5α
Ampicillin>256>256>256>256>256>2562
Amoxicillin-clavulanic acida8323163232
Ticarcillin>256>256>256>256>256>2564
Ticarcillin-clavulanic acidb6>2561.516>25684
Piperacillin812481282
Piperacillin-tazobactamc1112211
Cefoxitin333164832
Ceftazidime8>2560.50.754320.12
Aztreonam0.09420.0320.0320.09420.032
Cefotaxime11.50.750.1250.12530.032
Imipenem0.250.1250.501.50.500.250.064
Meropenem0.0160.0160.0320.0940.0470.0230.008
  • a Penicillin/inhibitor ratio of 2:1.

  • b Inhibitor was present at a fixed concentration of 2 μg/ml.

  • c Inhibitor was present at a fixed concentration of 4 μg/ml.