TABLE 2.

MICs (determined by Etest) of several β-lactam and non-β-lactam antibiotics for the epidemic CTX-M-1-producing multiresistant K. pneumoniae strain, the two carbapenem-resistant mutants, and the E. coli transformant harboring the CTX-M-1-encoding plasmid pAMR-1

AntibioticMIC (μg/ml) for:
CTX-M-1-producing K. pneumoniae epidemic strainaK. pneumoniae carbapenem-resistant mutantsE. coli XL1-BlueE. coli XL1-Blue (pAMR-1)
KpCR-1KpCR-2
Ampicillin>256>256>2564>256
Amoxycilin + clavulanate16-32>25632416
Ticarcillin>256>256>2568>256
Piperacillin>256>256>2561.5>256
Piperacillin + tazobactam32->256>256>2561.516
Cefoxitin6-48>25612828
Ceftazidime16-128>256>2560.524
Ceftazidime + clavulanate1.5-4>4>40.52
Cefotaxime>256>256>2560.19>256
Cefotaxime + calvulanate0.38-1>1>1<0.250.5
Cefepime32->256>256>2560.125128
Cefepime + clavulanate0.094-0.5>4>40.0940.19
Aztreonam48->256>256>2560.125>256
Imipenem0.38-0.58120.380.38
Meropenem0.094-0.2516160.0160.047
Ertapenem0.094-1.5>32>320.0120.125
Gentamicin12-2432480.198
Tobramycin16-3248960.12516
Amikacin1.5-3360.750.75
Ciprofloxacin>32>32>320.0470.047
Trimethoprim + sulfamethoxazole>32>32>320.0120.032
Tetracyclines>256>256>256>256>256
  • a Range of MICs for five randomly selected isolates, each recovered from a different patient at different periods of the outbreak.