TABLE 3.
Influence of the cloned oprM and mexAB genes on the antibiotic susceptibility of P. aeruginosaa
| Strain/plasmid | MIC (μg/ml)b | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| CAR | CPZ | CEF | CPM | NOR | CIP | NOV | ERY | TET | IMP | |
| PAO6609 | 32 | 4 | 1 | 2 | 1 | 0.25 | 256 | 512 | 16 | 1 |
| K1032/pMMB206 | 1 | 0.5 | 0.25 | 0.25 | 0.25 | 0.03 | 16 | 64 | 1 | 1 |
| K1032/pQZ05 | 1 | 0.5 | 1 | 0.5 | 1 | 0.12 | 16 | 512 | 2 | 1 |
| K1032/pQZ06 | 1 | 0.5 | 0.25 | 0.25 | 0.25 | 0.03 | 16 | 64 | 1 | 1 |
| K1032/pQZ05 + pQZ06 | 32 | 4 | 1 | 0.5–1 | 1 | 0.25 | 256 | 512 | 8 | 1 |
| PAO1 | 32 | 8 | 1 | 1 | 0.5 | 0.25 | 256 | 256 | 16 | —c |
| K1119/pMMB206 | 4 | 0.5 | 0.06 | 0.06 | 0.12 | 0.12 | 64 | 128 | 0.5 | — |
| K1119/pQZ05 | 4 | 0.5 | 0.5 | 1 | 0.25 | 0.05 | 64 | 512 | 8 | — |
| ML5087 | 32 | 8 | 1 | 1 | 0.5 | 0.25 | 512 | 256 | 16 | — |
| K1121/pMMB206 | 1 | 0.5 | 0.25 | 0.25 | 0.25 | 0.12 | 4 | 64 | 1 | — |
| K1121/pQZ05 | 1 | 0.5 | 1 | 1 | 0.5 | 0.25 | 4 | 512 | 8 | — |
| K1115/pMMB206 | 1 | 0.5 | 0.25 | 0.125 | 0.25 | 0.12 | 4 | 64 | 1 | — |
| K1115/pQZ05 | 1 | 0.5 | 0.5 | 0.5 | 0.5 | 0.25 | 4 | 512 | 8 | — |
The ΔmexAB-oprM strains K1032 (derived from PAO6609), K1119 (derived from PAO1), and K1121 (derived from ML5087) and the ΔmexAB-oprM ΔmexCD-oprJ strain K1115 (derived from ML5087) were reconstituted with the pMMB206-derived oprM (pQZ05) and mexAB (pQZ06) plasmids, and the influences on antibiotic susceptibilities were assessed as outlined in Materials and Methods.
CAR, carbenicillin; CPZ, cefoperazone; CEF, cefepime; CPM, cefpirome; NOR, norfloxacin; CIP, ciprofloxacin; NOV, novobiocin; ERY, erythromycin; TET, tetracycline; IMP, imipenem. Twofold differences were confirmed as significant by performing agar diffusion assays where the more susceptible strain elicited a zone of inhibition which was ≥25% larger than that of the more resistant strains at a set concentration of antibiotic.
Not determined.