TABLE 1.
Modal MICs and susceptibility categorization (CLSI/EUCAST) of study isolates and antibioticsa
| Isolate | Antibiotic MIC (μg/ml) (categorical interpretation via CLSI/EUCAST breakpoints)b,c |
|||||
|---|---|---|---|---|---|---|
| Meropenem | Imipenem | Levofloxacin | Cefazolin | Cefepime | Piperacillin-tazobactam | |
| E. coli ATCC 25922 | ≤0.063 (S/S) | 0.25 (S/S) | ≤0.063 (S/S) | 2 (S/–) | ≤0.063 (S/S) | 4/4 (S/S) |
| K. pneumoniae ATCC 13883 | 0.25 (S/S) | NT | NT | 4 (I/–) | 0.125 (S/S) | 4/4 (S/S) |
a
S, susceptible; I, intermediate; NT, not tested; –, unavailable.
b
CLSI susceptibility breakpoints for E. coli and K. pneumoniae are ≤1 μg/ml (meropenem and imipenem), ≤0.5 μg/ml (levofloxacin), ≤2 μg/ml (cefazolin), ≤2 μg/ml (cefepime), and ≤16/4 μg/ml (piperacillin-tazobactam) (15).
c
EUCAST susceptibility breakpoints for E. coli and K. pneumoniae are ≤2 μg/ml (meropenem and imipenem), ≤0.5 μg/ml (levofloxacin), ≤1 μg/ml (cefepime), and ≤8/4 μg/ml (piperacillin-tazobactam). EUCAST has not currently published a susceptibility breakpoint for cefazolin (16).