TABLE 1.

MICs of various β-lactams for P. mirabilis NO-113 and E. coli DH5α(pPm87), producing the TEM-87 enzymea

Antibiotic(s)MIC (μg/ml) for:
P. mirabilis NO-113bE. coli DH5α(pPm87)cE. coli DH5αd
Ampicillin>64>644
Amoxicillin-clavulanatee16164
Piperacillin>256>2561
Piperacillin-tazobactamf80.50.5
Cefazolin>64322
Cefotaxime21≤0.06
Ceftazidime64>640.12
Cefepime164≤0.06
Aztreonam32640.12
  • a The in vitro susceptibility of E. coli DH5α is also shown for comparison.

  • b The enzymes detected in the crude extract of this strain by analytical IEF had pIs of 5.8, 7.1, and 8.7.

  • c The enzyme detected in the crude extract of this strain by analytical IEF had a pI of 5.8.

  • d No enzymes were detected in the crude extract of this strain.

  • e Clavulanic acid was used at a 1:2 ratio.

  • f Tazobactam was used at a fixed concentration of 4 μg/ml.