TABLE 1.
MICs for Escherichia coli strainsa
| Compound (MIC unit) | MIC for strainb: |
|||||||
|---|---|---|---|---|---|---|---|---|
| W3110 | BC202 | ΔmdfA mutant | BC202 M | ΔemrE mutant | BC202E | ΔacrB mutant | BC202A | |
| SDS (%) | >1 | >1 | >1 | >1 | >1 | >1 | 0.5 | 0.06 |
| CAM (μg/ml) | 6.0 | 6.0 | 3.0 | 3.0 | 6.0 | 6.0 | 0.4 | 0.4 |
| BC (μg/ml) | 25 | 6.3 | 6.3 | 6.3 | 12.5 | 3.1 | 0.8 | 0.2 |
| NA (μg/ml) | 6.0 | 3.0 | 6.0 | 3.0 | 6.0 | 1.6 | 3.0 | 0.4 |
| CTAB (μg/ml) | 12.5 | 6.3 | 6.3 | 3.1 | 6.3 | 1.6 | 1.6 | 1.6 |
| MV (μg/ml) | 100 | 25 | 100 | 25 | 25 | 12.5 | 100 | 25 |
| Acr (μg/ml) | 100 | 12.5 | 50 | 6.3 | 25 | 6.3 | 6.3 | 0.8 |
| EthBr (μg/ml) | 400 | 25 | 200 | 12.5 | 200 | 12.5 | 3.1 | 0.8 |
| Erythro (μg/ml)c | 100 | 50 | 100 | 50 | 100 | 50 | 6.3 | 3.1 |
| Cipro (ng/ml)c | 5.0 | 2.5 | 5.0 | 2.5 | 5.0 | 2.5 | 1.25 | 0.3 |
| Norflox (ng/ml)c | 40 | 20 | 40 | 20 | 40 | 20 | 20 | 5.0 |
| Ox (μg/ml) | 400 | 200 | ND | ND | ND | ND | 25 | 3.1 |
| Clox (μg/ml) | 400 | 200 | ND | ND | ND | ND | 25 | 3.1 |
| Pip (μg/ml) | 2 | 0.5 | ND | ND | ND | ND | 0.25 | 0.03 |
W3110 (parent), BC202, and mutants with efflux pump mutations in either the W3110 (ΔmdfA, ΔemrE, and ΔacrB) or BC202 (BC202M, BC202E, and BC202A) background strain were grown in liquid culture in the presence of a series of dilutions of the indicated compounds. Abbreviations: SDS, sodium dodecyl sulfate; CAM, chloramphenicol; BC, benzalkonium chloride; NA, nalidixic acid; CTAB, cetyl trimethyl ammonium bromide; MV, methyl viologen; Acr, acriflavine hydrochloride; EthBr, ethidium bromide; Erythro, erythromycin; Cipro, ciprofloxacin; Norflox, norfloxacin; Ox, oxacillin; Clox, cloxacillin; Pip, piperacillin; ND, not determined.
In strain BC202, increased sensitivity to the indicated compounds is shown in italic. In strains BC202M, BC202E, and BC202A, additive or synergistic effects are shown in bold.
BC202 was not sensitive to erythromycin, ciprofloxacin, and norfloxacin on plates (Fig. 1 and data not shown) but was slightly sensitive in liquid culture.