Table 4.
Comparison of the PK–PD, CLSI and EUCAST breakpoints (mg/L) for Gram-negative aerobic bacteriaa
| EUCAST | |||||
|---|---|---|---|---|---|
| Antimicrobial regimen | PK–PDb | CLSIc | EB | PA | AB |
| Piperacillin-tazobactam | 4/4–16/4 | 16/4 | — | — | — |
| Cefepime | 1–4 | 8 | 1 | 8 | — |
| Ceftizoxime | 4 | 8 | — | — | — |
| Ceftriaxone | 0.5 | 8 | 1 | — | — |
| Ceftazidime | 4–8 | 8 | 1 | 8 | — |
| Ertapenem | 0.25 | 2 | 0.5 | — | — |
| Imipenem | 4 | 4 | 4 | 2 | 4 |
| Meropenem | 4 | 4 | 2 | 2 | 2 |
| Aztreonam | 4–8 | 8 | 1 | 1 | — |
| Gentamicin | 2 | 4 | 2 | 4 | 4 |
| Tobramycin | 2 | 4 | 2 | 4 | 4 |
| Ciprofloxacin | 0.125 | 1 | 0.5 | 0.5 | 1 |
| Levofloxacin | 0.25–0.5 | 2 | 1 | 1 | 1 |
EB, Enterobacteriaceae; PA, P. aeruginosa; AB, A. baumannii.
PK–PD breakpoints are regimen-dependent and species-independent (see the Methods section); therefore, the range represents the regimen-dependency of PK–PD breakpoints: piperacillin-tazobactam (3.375 g every 6 h, 4/4 mg/L; 4.5 g every 6 h, 4/4 mg/L; 3.375 g every 4 h, 16/4 mg/L), cefepime (1 g every 12 h, 1 mg/L; 1 g every 8 h, 4 mg/L; 2 g every 12 h, 2 mg/L; 2 g every 8 h, 4 mg/L), ceftazidime (1 g every 8 h, 4 mg/L; 2 g every 8 h, 8 mg/L), aztreonam (1 g every 8 h, 4 mg/L; 2 g every 8 h, 8 mg/L) and levofloxacin (500 mg every 24 h, 0.25 mg/L; 750 mg every 24 h, 0.5 mg/L).
The CLSI breakpoints are consistent for all antibiotics evaluated against Enterobacteriaceae, P. aeruginosa and A. baumannii, except for piperacillin-tazobactam (breakpoint for P. aeruginosa, 64 mg/L). The CLSI does not have breakpoints for the following: P. aeruginosa (ertapenem) and A. baumannii (ceftizoxime, ertapenem, aztreonam).