TABLE 1.

MICs of β-lactams for M. morganii clinical isolates, derived AmpC hyperproducers, and E. coli strains harboring ampC from M. morganii

Antibiotic(s)MIC (μg/ml) for:
Wild-type strainsAmpC hyperproducersEscherichia coli strains
PP19PP29PP37PP19CPP29IIPP37BTCR192cTC192-2dTop10 F′
Ampicillin25664321,0241,0245125122562
Ampicillin-clavulanatea128/64128/6464/32512/256512/256256/128256/128128/642/1
Piperacillin160.250.25>64321664321
Piperacillin-tazobactamb10.0630.06332841680.5
Cephalothin>512>512>512>2,048>2,048>2,048>5122562
Cefoxitin328464166464162
Cefotaxime≤0.032≤0.032≤0.0321641620.5≤0.032
Ceftazidime10.50.5321664840.063
Cefoperazone112328160.250.25≤0.032
Cefepime≤0.008≤0.008≤0.008≤0.008≤0.008≤0.0080.0080.0160.016
Imipenem222221220.063
Aztreonam≤0.032≤0.032≤0.0320.50.50.0640.50.50.063
  • a Used at a ratio of 2:1.

  • b Fixed concentration of 4 μg/ml.

  • c Strain harboring pMCR19-2 (ampC, ampR from M. morganii strain PP19).

  • d Strain harboring pMC192-2 (ampC from M. morganii strain PP19).