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Table 1 MIC range, MIC 50 (mg/L) and MIC 90 (mg/L) values of 21 antimicrobial agents for Ec-ESBL and Ec-MRnoB isolates, and percentages of resistant isolates to the indicated agents (EUCAST breakpoints, except where indicated)

From: Molecular characterization of multiresistant Escherichia coli producing or not extended-spectrum β-lactamases

  Ec-ESBL (N=100) Ec-MRnoB (N=100)
Agent Range MIC50 MIC90 %R Range MIC50 MIC90 %R
Amoxicillin 64-≥256 ≥256 ≥256 100 2-≥256 ≥256 ≥256 99
Amoxicillin-Clavulanic acid 8-16 4 8 41 8-≥128 8 32 83
Piperacillin 32-≥64 ≥64 ≥64 100 ≤16-≥64 ≥64 ≥64 84
Piperacillin-Tazobactam ≤0.5-≥256 4 16 16 ≤0.25-≥256 2 4 6
Cefoxitin a ≤2-32 ≤2 8 5 ≤2-≥32 4 8 8
Cefotetan a ≤1-8 ≤1 ≤1 0 ≤1-≥32 ≤1 ≤1 2
Cefotaxime 32-≥128 ≥128 ≥128 100 ≤0.5-128 ≤0.5 ≤0.5 5
Ceftazidime ≤0.5-≥128 2 16 23 ≤0.5-128 ≤0.5 ≤0.5 8
Cefepime ≤1-≥32 ≥32 ≥32 96 ≤1-4 ≤1 <1 1
Aztreonam 2-≥64 16 ≥64 96 ≤0.5-32 ≤0.5 ≤0.5 6
Imipenem ≤0.5-1 ≤0.5 ≤0.5 0 ≤0.5-2 ≤0.5 ≤0.5 0
Meropenem ≤0.5 ≤0.5 ≤0.5 0 ≤0.5 ≤0.5 ≤0.5 0
Gentamicin ≤0.5-≥256 1 32 19 0.5-≥256 64 256 96
Tobramycin 0.5-256 1 8 17 ≤0.25-256 8 32 89
Amikacin ≤0.5-8 2 4 0 1-8 2 4 0
Nalidixic acid a 1-≥256 ≥256 ≥256 89 1-≥256 ≥256 ≥256 98
Ciprofloxacin a ≤0.5-≥256 16 128 74 ≤0.25-≥256 32 128 93
Tetracycline a 0.5-≥256 256 256 80 ≤0.25-256 256 256 84
Doxycycline a ≤0.5-128 16 64 76 ≤0.25-128 32 64 79
Tigecycline b ≤0.5-1 ≤0.5 ≤0.5 0 ≤0.25-0.5 ≤0.25 ≤0.25 0
Trimethoprim-Sulfamethoxazole ≤0.5-≥32 ≥32/608 ≥32/608 67 ≤0.5-≥32 ≥32/608 ≥32/608 98
  1. a CLSI 2011 breakpoints. b FDA breakpoints.