TABLE 1.

Susceptibility testing results obtained by each method and interpretative criteria for the 18 VIM-1-producing K. pneumoniae isolates

Method and antibioticNo. of isolates inhibited at the following concn (mg/liter)a: MIC (mg/liter)bNo. of isolates within the following interpretive criterionc:
0.51248163264128>128Range50%90%SusceptibleIntermediateResistant
Microdilution
    Imipenem[1151]18->1288320018
    Meropenem[1310311]0.5-128244104
    Ertapenem[21311]1-64280018
Etest
    Imipenem5362]20.75->323>32567
    Meropenem3131]10.38->3211.51611
    Ertapenem1961]10.75->322120117
Wider
    Imipenem[653]4≤1->84>86012
    Meropenem[8233]2≤1->82>8828
  • a Left and right brackets indicate the lowest and highest concentrations tested, respectively.

  • b 50% and 90%, MICs at which 50 and 90% of the isolates, respectively, were inhibited.

  • c The CLSI breakpoints for susceptibility and resistance were ≤1 mg/liter and ≥4 mg/liter for imipenem and meropenem and ≤0.25 mg/liter and ≥1 mg/liter for ertapenem, respectively.