TABLE 2

In vitro activity of imipenem-relebactam and comparative antimicrobial agents against non-Proteeae Enterobacteriaceae collected as part of the SMART global surveillance program in the United States in 2016

Phenotype (n)Antimicrobial agentMIC determination (μg/ml)MIC interpretation
MIC50MIC90MIC range% susceptible% intermediate% resistant
All (3,143)Imipenem-relebactama0.120.5≤0.06 to >3299.10.50.4
Imipenem≤0.51≤0.5 to >3295.92.22.0
Ertapenem≤0.060.12≤0.06 to >496.11.62.4
Amikacin≤4≤4≤4 to >3299.60.30.2
Aztreonam≤1>16≤1 to >1683.81.914.2
Cefepimeb≤14≤1 to >3288.53.87.8
Ceftazidime≤116≤1 to >3285.62.312.2
Ceftriaxone≤1>32≤1 to >3279.81.918.2
Ciprofloxacin≤0.25>2≤0.25 to >280.51.518.0
Colistinc≤1≤1≤1 to >491.38.7
Piperacillin-tazobactam≤232≤2 to >6489.94.65.5
Imipenem nonsusceptible (130)Imipenem-relebactama0.52≤0.06 to >3278.512.39.2
Imipenem2322 to >32052.347.7
Ertapenem≤0.06>4≤0.06 to >466.91.531.5
Amikacin≤416≤4 to >3297.71.50.8
Aztreonam≤1>16≤1 to >1664.61.533.9
Cefepimeb≤1>32≤1 to >3271.56.921.5
Ceftazidime≤1>32≤1 to >3266.93.130.0
Ceftriaxone≤1>32≤1 to >3260.83.935.4
Ciprofloxacin≤0.25>2≤0.25 to >276.25.418.5
Colistinc>4>4≤1 to >441.558.5
Piperacillin-tazobactam≤2>64≤2 to >6467.75.426.9
Cefepime nonsusceptible (363)Imipenem-relebactama0.120.25≤0.06 to >3298.40.80.8
Imipenem≤0.52≤0.5 to >3289.81.48.8
Ertapenem≤0.06>4≤0.06 to >476.98.314.9
Amikacin≤416≤4 to >3297.31.90.8
Aztreonam>16>16≤1 to >168.57.484.0
Cefepimeb32>324 to >32032.867.2
Ceftazidime16>32≤1 to >3217.614.667.8
Ceftriaxone>32>32≤1 to >321.70.398.1
Ciprofloxacin>2>2≤0.25 to >224.26.369.4
Colistinc≤1≤1≤1 to >496.13.9
Piperacillin-tazobactam16>64≤2 to >6460.611.028.4
Ceftazidime nonsusceptible (454)Imipenem-relebactama0.120.5≤0.06 to >3298.70.70.7
Imipenem≤0.51≤0.5 to >3290.51.87.7
Ertapenem0.124≤0.06 to >478.07.914.1
Amikacin≤48≤4 to >3298.01.50.4
Aztreonam>16>16≤1 to >165.55.788.8
Cefepimeb8>32≤1 to >3234.117.448.5
Ceftazidime32>328 to >32015.984.1
Ceftriaxone>32>32≤1 to >321.51.397.1
Ciprofloxacin>2>2≤0.25 to >242.55.152.4
Colistinc≤1≤1≤1 to >493.46.6
Piperacillin-tazobactam32>64≤2 to >6448.724.726.7
Piperacillin-tazobactam nonsusceptible (319)Imipenem-relebactama0.120.5≤0.06 to >3298.10.90.9
Imipenem≤0.54≤0.5 to >3286.82.211.0
Ertapenem0.25>4≤0.06 to >469.911.019.1
Amikacin≤48≤4 to >3297.51.60.9
Aztreonam>16>16≤1 to >1624.53.871.8
Cefepimeb2>32≤1 to >3255.218.226.7
Ceftazidime32>32≤1 to >3227.04.468.7
Ceftriaxone32>32≤1 to >3221.00.978.1
Ciprofloxacin≤0.25>2≤0.25 to >258.94.736.4
Colistinc≤1≤1≤1 to >491.98.2
Piperacillin-tazobactam>64>6432 to >64045.554.6
MDR (452)Imipenem-relebactama0.120.5≤0.06 to >3298.20.90.9
Imipenem≤0.52≤0.5 to >3288.92.48.6
Ertapenem0.124≤0.06 to >477.98.014.2
Amikacin≤48≤4 to >3297.81.60.7
Aztreonam>16>16≤1 to >163.38.288.5
Cefepimeb16>32≤1 to >3226.320.653.1
Ceftazidime32>32≤1 to >3210.013.376.8
Ceftriaxone>32>32≤1 to >322.70.496.9
Ciprofloxacin>2>2≤0.25 to >235.06.059.1
Colistinc≤1≤1≤1 to >491.28.9
Piperacillin-tazobactam32>64≤2 to >6447.126.126.8
  • a Breakpoints for imipenem-relebactam have not been defined. For the purpose of comparison, MICs were interpreted using CLSI imipenem MIC breakpoints for Enterobacteriaceae (susceptible, ≤1 μg/ml; intermediate, 2 μg/ml; resistant, ≥4 μg/ml) (24).

  • b For cefepime, the intermediate category is replaced by the “susceptible-dose dependent” category (24).

  • c CLSI breakpoints for colistin have not been defined against Enterobacteriaceae, and MICs were interpreted using EUCAST breakpoints (26).