TABLE 1.

MICs of β-lactams for S. marcescens HD and S3 strains and for recombinant E. coli DH10B(pBK-HD) and E. coli DH10B(pBK-S3)

β-Lactam(s)fMIC (μg/ml)
S. marcescens HDaS. marcescens S3bE. coli DH10B(pBK-HD)cE. coli DH10B(pBK-S3)dE. coli DH10B(pBK-TEM-1)eE. coli DH10B
Amoxicillin>512>512>512>512>5122
Amoxicillin-CLA256>5122562565122
Ticarcillin>512328128>5121
Ticarcillin-CLA256328128>5121
Piperacillin51216256256641
Piperacillin-TZB328128128321
Cephalothin>512>512>512>51284
Cefoxitin81612812822
Cefuroxime1285125121280.50.5
Ceftriaxone20.25168<0.06<0.06
Cefotaxime20.25168<0.06<0.06
Ceftazidime640.0651216<0.06<0.06
Aztreonam0.50.060.250.060.060.06
Cefepime320.0651220.060.06
Cefpirome80.066420.060.06
Imipenem0.060.060.060.060.060.06
  • a S. marcescens isolate HD produced β-lactamases AmpC HD and TEM-1.

  • b S. marcescens isolate S3 reference strain produced β-lactamase AmpC S3.

  • c The recombinant E. coli DH10B(pBK-HD) strain produced β-lactamase AmpC HD.

  • d The recombinant E. coli DH10B(pBK-S3) strain produced β-lactamase AmpC S3.

  • e The recombinant E. coli DH10B(pBK-TEM-1) strain produced β-lactamase TEM-1.

  • f CLA, clavulanic acid at 2 μg/ml; TZB, tazobactam at 4 μg/ml.