Table 3.

β-Lactamase activity of M. morganii 1 with or without pNH5 (ampD of E. cloacae) and E. coli MC4100 harboring either recombinant plasmid pAC-1 (ampR and ampC genes) or pAC-2 (ampC gene)

Strainβ-Lactamase activity (mU/mg of protein)a
Basal levelInduced
M. morganii 1b1,4301,350
M. morganii 1(pNH5)b8400
E. coliMC4100(pAC-1)c2001,350
E. coliMC4100(pAC-2)c1,1601,100
  • a One unit of β-lactamase is defined as 1 μmol of cephalothin hydrolyzed per min. The β-lactamase activities are geometric mean determinations for three independent cultures. The standard deviations were within 10%.

  • b Imipenem (0.5 μg/ml) was used as the inducer.

  • c Cefoxitin (4 μg/ml) was used as the inducer.