TABLE 1.

MICs of β-lactams conferred in E. coli JM83 by the E. cloacae P99 β-lactamase and its mutants with replacement of Leu-293

Amino acid at res- idue 293MIC (μg/ml) of indicated β-lactama
AMPCAZFEPCROCFPPIPATMLOR
Noneb40.125<0.015<0.03<0.060.5<0.034
Leuc1,024640.512812812864512
Pro25625683212864864
Gly51225626412812816512
Ala25612826412812816512
Val51212826412825632256
Ser51212826412812816256
Cys5121281646412832256
Asn512128132646432512
Glu5126413212812816256
Met512128112812812832512
Asp256128243282512
Arg256320.5643212864128
Phe256320.5641286464256
His256160.2532323264128
Tyr256320.25321283264256
Lys256320.2564326464128
  • a Abbreviations: AMP, ampicillin; CAZ, ceftazidime; FEP, cefepime; CRO, ceftriaxone; CFP, cefoperazone; PIP, piperacillin; ATM, aztreonam; LOR, cephaloridine.

  • b E. coli JM83 recipient strain.

  • c Wild-type E. cloacae P99 β-lactamase.