TABLE 3.

MICs of antibiotics for strain PAO1 and nagZ and/or ampD null mutants of P. aeruginosa

StrainMIC (μg/ml)a
ATM (≤8->16)CAZ (≤8->16)PIP (≤64->64)PIP-TZ (≤64->64)FEP (≤8->16)IMP (≤4->8)FOX (NA)CIP (≤1->2)
PAO11b1b110.531,600b0.2b
PAΔnagZ0.25b0.5b11.50.382800b0.2b
PAΔDDh2Dh32448>256≥256121.53,200b0.2b
PAΔDDh2Dh3nagZ412241631.52,400b0.2b
Complementation with wild-type nagZ
    PAΔnagZ(pUCP27)600b
    PAΔnagZ(pUCPnagZ)1,200b
    PAΔDDh2Dh3nagZ(pUCP27)61216
    PAΔDDh2Dh3nagZ(pUCPnagZ)2448256
  • a ATM, aztreonam; CAZ, ceftazidime; FEP, cefepime; PIP, piperacillin; PIP-TZ, piperacillin-tazobactam; IMP, imipenem; FOX, cefoxitin; CIP, ciprofloxacin; NA, not available. MICs were determined by using Etest strips, unless otherwise indicated. CLSI resistance breakpoints (in μg/ml) are shown in parentheses after the abbreviation for each antibiotic. All measurements were performed in triplicate.

  • b MICs were determined by broth microdilution, as recommended by the CLSI (see Results).