Table 3.

PTA at existing CLSI breakpoints^a

Antimicrobial and dosing regimen	PTA (%)
Piperacillin-tazobactam
3.375 g every 4 h	91
3.375 g every 6 h	6
4.5 g every 6 h	21
Cefepime
1 g every 12 h	2
1 g every 8 h	57
2 g every 12 h	21
2 g every 8 h	87
Ceftizoxime
1 g every 8 h	5
Ceftriaxone
1 g every 24 h	0
2 g every 24 h	17
Ceftazidime
1 g every 8 h	68
2 g every 8 h	98
Ertapenem
1 g every 24 h	59
Imipenem
500 mg every 6 h	99
Meropenem
1 g every 8 h	98
Aztreonam
1 g every 8 h	26
2 g every 8 h	90
Gentamicin
5 mg/kg every 24 h	20
Tobramycin
5 mg/kg every 24 h	20
Ciprofloxacin
400 mg every 8 h	0
400 mg every 12 h	0
Levofloxacin
500 mg every 24 h	0
750 mg every 24 h	0

^aThe 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). Table 3 reflects the PTA for piperacillin-tazobactam when a breakpoint of 16 mg/L was used. If a breakpoint of 64 mg/L were used instead (i.e. P. aeruginosa), the corresponding probabilities of target attainment for piperacillin-tazobactam would be: 3.375 g every 4 h (0%), 3.375 g every 6 h (0%) and 4.5 g every 6 h (0%).