Table 6.

β-Lactamase inducibility in E. cloacae 8009 and various transformants

Expt. no. and strainPhenotypeInduceraβ-Lactamase activitybInducibility and inducibility ratioc
μM/min · mg of proteinRatiod
Expt 1
E. cloacae 8009AmpA AmpR3401.0Inducible
 E. coliDH10B<1<0.003Constitutive
 E. coli DH10B/pFCX300L (TF-L)AmpA AmpR220.064Inducible
 E. coliDH10B/pFCX300M (TF-M)AmpA AmpR1190.35Inducible
 E. coliDH10B/pFCX301 (TF-L7)AmpA AmpR7002.1Inducible
 E. coliDH10B/pFCX302 (TF-M4)AmpA AmpR6201.9Inducible
Expt 2
 E. cloacae 8009AmpA AmpR2601.0Inducible
 E. coliDH10B/pFCX310 (TF2-2)AmpA2801.1Constitutive
 E. coliDH10B/pFCX320 (TF2-3)AmpA3501.3Constitutive
  • a The inducer was imipenem-cilastatin at 0.1 μg/ml.

  • b Cefotaxime (100 μM) was used as a substrate.

  • c Induced activity/uninduced activity for each set.

  • d Activity of extract/uninduced activity ofE. cloacae 8009.

  • e Nitrocefin was used as the substrate for calculation of the inducibility ratio for this strain.