TABLE 3.
Apparent contribution of multidrug efflux to MIC
| β-Lactam | MICwt/MICΔacrAB in E. coli K-12a | MICwt/MICacr in S. typhimuriumb | Side chain lipophilicityc |
|---|---|---|---|
| Cloxacillin | 128 | 256 | 890 |
| Oxacillin | 512 | ND | ND |
| Mezlocillin | 32 | ND | ND |
| Piperacillin | 16 | ND | ND |
| Cefuroxime | 16 | ND | 55d |
| Carbenicillin | 4 | 4 | 80 |
| Penicillin G | 2 | 32 | 270 |
| Cefoxitin | 4 | 4 | 130 |
| Cephaloridine | 2 | 2 | 130 |
| Ceftriaxone | 1 | 2 | 6 |
| Cefsulodin | 1 | 1 | 80e |
| Cefmetazole | 1 | 1 | 2 |
| Cefazolin | 1 | 1 | 0.5 |
| Cefepime | 1 | ND | 6 |
| Cefpirome | 1 | 1 | 6 |
| Imipenem | 1 | 1 | 0.3 |
a
Based on Table 1 data. wt, wild type.
b
From reference 18.
c
Expressed as the calculated octanol-water partition coefficient. From reference 18.
d
Calculated as described in reference 18.
e
Although the phenyl group shows a moderate lipophilicity, insertion of this side chain may be prevented by the presence of a negatively charged group next to it (18).