TABLE 6.
Activities and spectra of activity of 15 β-lactam antimicrobial agents tested against the four most prevalent causes of gram-negative bacteremia in the United States (34% of all bacteremic episodes)
| Antimicrobial class and agent tested | Activitya againstb:
|
|||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
E. coli (769)
|
Klebsiella (311)
|
P. aeruginosa (189)
|
Enterobacter (151)
|
|||||||||
| MIC range | MIC50/ MIC90 | % S | MIC range | MIC50/ MIC90 | % S | MIC range | MIC50/ MIC90 | % S | MIC range | MIC50/ MIC90 | % S | |
| Penicillins | ||||||||||||
| Ampicillin-amoxicillin | 0.25–>16 | 8/16 | 52.4 | 4–>16 | >16/>16 | 2.7 | 16–>16 | >16/>16 | 0.0 | 4–>16 | >16/>16 | 1.4 |
| Piperacillin | ≤1–>128 | 2/>128 | 57.0 | ≤1–>128 | 8/>128 | 80.7 | ≤1–>128 | 4/64 | 93.0 | ≤1–>128 | 4/>128 | 63.9 |
| Ticarcillin | ≤1–>128 | 8/>128 | 53.6 | ≤1–>128 | >128/>128 | 2.3 | ≤1–>128 | 32/128 | 86.6 | ≤1–>128 | 8/>128 | 59.2 |
| Amoxicillin-clavulanate | 0.5–>16 | 8/16 | 68.8 | 1–>16 | 4/16 | 89.7 | 2–>16 | >16/>16 | 1.6 | 4–>16 | >16/>16 | 2.8 |
| Ticarcillin-clavulanate | ≤1–>128 | 4/64 | 67.1 | ≤1–>128 | 4/32 | 88.2 | ≤1–>128 | 32/128 | 87.6 | ≤1–>128 | 8/>128 | 58.5 |
| Piperacillin-tazobactam | ≤0.5–>64 | 2/4 | 95.5 | ≤0.5–>64 | 4/16 | 94.0 | ≤0.5–>64 | 4/32 | 92.4 | ≤0.5–>64 | 4/>64 | 68.8 |
| Cephalosporins | ||||||||||||
| Cefazolin | ≤2–>16 | ≤2/16 | 88.0 | ≤2–>16 | ≤2/>16 | 86.0 | 1–>16 | >16/>16 | 1.1 | ≤2–>16 | >16/>16 | 1.4 |
| Cefuroxime | ≤0.12–>16 | 4/8 | 94.9 | 0.25–>16 | 4/8 | 90.2 | >16 | >16/>16 | 0.0 | 0.5–>16 | >16/>16 | 29.9 |
| Cefoxitin | ≤0.25–>32 | 4/8 | 93.0 | ≤0.25–>32 | 4/8 | 90.5 | 0.5–>32 | >32/>32 | 1.1 | 8–>32 | >32/>32 | 2.0 |
| Cefotaxime-ceftriaxone | ≤0.25–>32 | ≤0.25/≤0.25 | 98.3 | ≤0.25–>32 | ≤0.25/≤0.25 | 97.3 | 0.5–>32 | >32/>32 | 18.5 | ≤0.25–>32 | 0.5/>32 | 69.5 |
| Ceftazidime | ≤0.12–>16 | ≤0.12/0.5 | 98.0 | ≤2–>16 | 0.25/1 | 96.4 | 1–>16 | 2/16 | 87.1 | ≤0.25–>16 | 0.5/>16 | 69.4 |
| Cefepime | ≤0.12–16 | ≤0.12/0.25 | 99.3 | ≤0.12–>16 | ≤0.12/0.25 | 98.7 | 0.5–>16 | 2/16 | 87.0 | ≤0.12–>16 | ≤0.12/4 | 99.3 |
| Others | ||||||||||||
| Aztreonam | ≤0.12–>16 | ≤0.12/≤0.12 | 97.6 | ≤0.12–>16 | ≤0.12/0.25 | 96.1 | 0.25–>16 | 8/>16 | 77.4 | ≤0.12–>16 | ≤0.12/>16 | 70.7 |
| Imipenem | ≤0.06–2 | 0.25/0.5 | 99.5 | ≤0.06–4 | 0.25/0.5 | 100 | 0.12–>8 | 2/8 | 88.0 | ≤0.06–8 | 0.5/2 | 98.6 |
| Meropenem | ≤0.06–1 | ≤0.06/≤0.06 | 99.6 | ≤0.06–2 | ≤0.06/≤0.06 | 100 | ≤0.06–>8 | 0.5/2 | 95.2 | ≤0.06–>8 | ≤0.06/0.25 | 99.3 |
a
MIC50, MIC90, and % S are as defined for Table 2. MIC units are micrograms per milliliter.
b
Numbers in parentheses are numbers of isolates.