TABLE 1.

β-Lactamase activities of E. cloacae clinical isolates and MICs of ceftazidime

Strainβ-Lactamase activity (U/mg protein)aMIC of ceftazidime (μg/ml)β-Lactamase profileb
Clinical isolatesTransformantscClinical isolatesTransformantsc
KU634437.02 ± 0.5915.66 ± 0.2320.25
KU634524.13 ± 0.441.82 ± 0.04>128>128blaIMP
KU633914.64 ± 1.21<0.01640.125
KU632912.63 ± 0.130.05 ± 0.01>1281
KU632612.18 ± 0.43<0.01>1288
KU633111.95 ± 0.470.33 (0.07 ± 0.04)1280.5blaTEM
KU633211.50 ± 0.220.30 ± 0.01 (0.06 ± 0.01)1280.5blaTEM
KU63309.31 ± 0.070.02640.5
KU63257.56 ± 0.25<0.01320.125
KU63407.28 ± 0.130.05 ± 0.01640.25
KU63286.13 ± 0.090.05 ± 0.011280.5
KU63236.03 ± 0.14<0.01320.125
KU63415.76 ± 0.28<0.01321
KU63433.41 ± 0.232.97 ± 0.11 (1.43 ± 0.08)12864blaTOHO
KU63342.55 ± 0.080.34 ± 0.02321
KU63460.88 ± 0.010.39 ± 0.01 (0.21 ± 0.02)641
KU63270.51 ± 0.04<0.01160.5
KU63380.41 ± 0.010.02 ± 0.01320.5
KU63360.39 ± 0.010.03 ± 0.01160.25
KU63240.31 ± 0.03<0.01160.5
KU63370.14<0.01320.25
KU32620.07 ± 0.01NTd0.25NTNT
  • 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. Values in parentheses indicate the activity determined in the presence of clavulanic acid (5 μg/ml).

  • b blaTEM, blaTOHO, and blaIMP indicate β-lactamase genotypes detected by PCR amplification in addition to chromosomal ampC.

  • c Strains transformed with plasmid pKU420 containing the wild-type ampD gene from E. coli.

  • d NT, not tested.