TABLE 4

In vitro activity of imipenem-relebactam and comparative antimicrobial agents against P. aeruginosa

Phenotypea (n)Antimicrobial agentMIC determination (μg/ml)MIC interpretation
MIC50MIC90MIC range% susceptible% intermediate% resistant
All (896)Imipenem-relebactama0.52≤0.06 to >3294.42.82.8
Imipenem116≤0.5 to >3274.75.120.2
Amikacin≤48≤4 to >3295.22.02.8
Aztreonam8>16≤1 to >1663.112.824.1
Cefepime432≤1 to >3273.813.412.8
Ceftazidime4>32≤1 to >3277.15.417.5
Ciprofloxacin≤0.25>2≤0.25 to >272.95.421.8
Colistin≤1≤1≤1 to >499.70.3
Piperacillin-tazobactam8>64≤2 to >6471.212.416.4
Imipenem nonsusceptible (227)Imipenem-relebactama280.25 to >3278.011.011.0
Imipenem16324 to >32020.379.7
Amikacin≤432≤4 to >3288.15.36.6
Aztreonam>16>16≤1 to >1633.015.951.1
Cefepime16>32≤1 to >3240.526.433.0
Ceftazidime8>32≤1 to >3250.710.638.8
Ciprofloxacin>2>2≤0.25 to >242.77.150.2
Colistin≤1≤1≤1 to >499.10.9
Piperacillin-tazobactam32>64≤2 to >6441.022.037.0
Cefepime nonsusceptible (235)Imipenem-relebactama14≤0.06 to >3282.18.59.4
Imipenem832≤0.5 to >3242.66.451.1
Amikacin≤432≤4 to >3286.46.07.7
Aztreonam>16>16≤1 to >1614.514.571.1
Cefepime16>3216 to >32051.148.9
Ceftazidime32>322 to >3224.711.164.3
Ciprofloxacin2>2≤0.25 to >247.78.543.8
Colistin≤1≤1≤1 to >499.60.4
Piperacillin-tazobactam>64>64≤2 to >6416.623.460.0
Ceftazidime nonsusceptible (205)Imipenem-relebactama14≤0.06 to >3282.48.39.3
Imipenem432≤0.5 to >3245.45.449.3
Amikacin≤432≤4 to >3287.34.97.8
Aztreonam>16>16≤1 to >169.814.276.1
Cefepime16>322 to >3213.738.148.3
Ceftazidime32>3216 to >32023.476.6
Ciprofloxacin2>2≤0.25 to >248.87.343.9
Colistin≤1≤1≤1 to >499.50.5
Piperacillin-tazobactam>64>64≤2 to >646.325.468.3
Piperacillin-tazobactam nonsusceptible (258)Imipenem-relebactama14≤0.06 to >3283.77.88.5
Imipenem432≤0.5 to >3248.15.446.5
Amikacin≤416≤4 to >3290.32.77.0
Aztreonam>16>16≤1 to >1610.116.773.3
Cefepime16>32≤1 to >3224.035.340.7
Ceftazidime32>322 to >3225.615.159.3
Ciprofloxacin1>2≤0.25 to >250.46.643.0
Colistin≤1≤1≤1 to >499.60.4
Piperacillin-tazobactam>64>6432 to >64043.057.0
MDR (264)Imipenem-relebactama14≤0.06 to >3282.28.79.1
Imipenem832≤0.5 to >3240.26.153.8
Amikacin≤432≤4 to >3287.55.37.2
Aztreonam>16>16≤1 to >168.720.570.8
Cefepime16>322 to >3219.739.041.3
Ceftazidime32>322 to >3224.616.359.1
Ciprofloxacin2>2≤0.25 to >242.48.349.2
Colistin≤1≤1≤1 to >498.91.1
Piperacillin-tazobactam>64>64≤2 to >6412.132.655.3
  • a Breakpoints for imipenem-relebactam have not been defined. For the purpose of comparison, MICs were interpreted using CLSI imipenem MIC breakpoints for P. aeruginosa (susceptible, ≤2 μg/ml; intermediate, 4 μg/ml; resistant, ≥8 μg/ml) (24).