TABLE 2.

β-Lactamase activities and MICs of ceftazidime for E. cloacae bearing ampR genes from clinical isolates

Strainβ-Lactamase activity (U/mg protein)aMIC (μg/ml) of ceftazidime
NoninducedInducedb
KU32620.07 ± 0.019.97 ± 0.230.25
KU3262/pKU4301.56 ± 0.11c14.40 ± 0.70c2
KU3262/pKU4311.35 ± 0.12c13.98 ± 0.30c8
KU3262/pKU4320.08 ± 0.0212.15 ± 2.670.125
  • a Values are the means ± SDs for three independent experiments. One unit of β-lactamase activity was defined as the amount that hydrolyzed 1 mmol of cephalothin in 1 min at 30°C.

  • b β-Lactamase was induced with imipenem at 1/4 of the MIC for KU3262 (0.125 μg/ml).

  • c P < 0.001 versus KU3262.