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. Author manuscript; available in PMC: 2010 Oct 12.
Published in final edited form as: J Antimicrob Chemother. 2008 Feb 4;61(3):621–628. doi: 10.1093/jac/dkm536

Table 5.

Cumulative frequency distribution for Enterobacteriaceae, P. aeruginosa and A. baumannii isolates from the 2005 MYSTIC worldwide database with the corresponding percentage susceptible using PK–PD (P), CLSI (C) and EUCAST (E) breakpointsa

Cumulative MIC (mg/L) distribution
Organisms No of isolates 0.125 0.25 0.5 1 2 4 8 16 32 64 Divergence in
% susceptibleb
Enterobacteriaceae
 Piperacillin-tazobactam 7099 2 5 20 33 60 75P 81P 85PC 89 91 10
 Cefepime 4486 68 74 78 81PE 84P 86P 88C 91 93 97 7
 Ceftizoximec 965 82 86 90 91 93 93P 94C 94 95 100 1
 Ceftriaxone 1517 84 84 87P 88E 88 89 91C 92 95 100 4
 Ceftazidime 7104 39 59 71 76E 79 82P 84PC 86 92 94 8
 Ertapenem 1517 94 96P 97E 98 98C 99 99 99 99 100 2
 Imipenem 7104 36 67 82 91 97 98PCE 99 99 100 100 0
 Meropenem 7104 92 94 97 99 99E 99PC 99 100 100 100 0
 Aztreonam 1602 4 4 87 87E 87 87P 90PC 93 100 100 3
 Gentamicin 5173 3 13 62 78 83PE 85C 87 92 94 96 2
 Tobramycin 5421 3 8 47 68 79PE 83C 85 91 95 97 4
 Ciprofloxacin 7103 70P 73 76E 80C 82 87 89 90 93 99 10
 Levofloxacin 1517 73 76P 80P 83E 84C 86 90 100 — — 8
P. aeruginosa
 Piperacillin-tazobactam 2395 1 1 5 9 22 47P 58P 68PC 75 80 21
 Cefepime 1833 1 1 3 17P 35P 51P 65CE 74 79 95 48
 Ceftizoximec 298 — < 1 < 1 1 2 2P 4C 7 21 100 2
 Ceftriaxone 589 < 1 < 1 1P 3 6 10 18C 29 47 100 17
 Ceftazidime 2397 1 2 5 24 51 65P 72PCE 78 86 88 7
 Imipenem 2397 2 4 19 44 62E 69PC 76 83 88 98 7
 Meropenem 2398 22 37 52 63 69E 75PC 81 85 89 99 6
 Aztreonam 609 < 1 1 11 11E 11 11P 74PC 88 99 100 63
 Gentamicin 1835 1 3 24 36 57P 67CE 73 80 83 84 10
 Tobramycin 1916 2 5 44 60 70P 73CE 75 80 82 84 3
 Ciprofloxacin 2398 41P 49 59E 65C 70 79 81 83 87 99 24
 Levofloxacin 589 4 32P 52P 61E 69C 78 83 100 — — 37
A. baumannii
 Piperacillin-tazobactam 669 8 10 14 16 18 22P 27P 33PC 36 46 11
 Cefepime 509 1 2 3 6P 14P 20P 27C 44 59 79 21
 Ceftriaxone 88 — — —P 2 3 5 18C 18 42 51 100 16
 Ceftazidime 669 1 2 3 5 10 23P 30PC 36 59 67 7
 Imipenem 669 9 25 39 54 63 67PCE 71 75 85 99 0
 Meropenem 669 8 19 35 54 61E 66PC 72 77 88 100 5
 Gentamicin 424 2 7 26 38 43P 49CE 57 72 77 81 6
 Tobramycin 578 2 6 24 34 43P 49CE 54 66 75 83 6
 Ciprofloxacin 669 18P 27 32 34CE 36 47 49 50 64 97 16
 Levofloxacin 88 36 41P 42P 43E 47C 58 69 100 — — 2
a

The multiple annotations for PK–PD breakpoints represent their dose-dependent nature: 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 does not have breakpoints for the following: P. aeruginosa (ertapenem) and A. baumannii (ceftizoxime, ertapenem and aztreonam), whereas the EUCAST does not have breakpoints for the following: Enterobacteriaceae (piperacillin-tazobactam and ceftizoxime), P. aeruginosa (piperacillin-tazobactam, ceftizoxime, ceftriaxone and ertapenem) and A. baumannii (piperacillin-tazobactam, cefepime, ceftizoxime, ceftriaxone, ceftazidime, ertapenem and aztreonam).

b

This column reflects the difference in percentage susceptible among the three different breakpoints (CLSI, EUCAST and PK–PD). Large discrepancies indicate that the percentage susceptible varies greatly depending upon which breakpoint is applied.

c

The most current MIC data available for ceftizoxime were from 2001.