TABLE 2.
Gradient plate analysis of abilities of E. coli MFP members to activate AcrB-mediated drug effluxa
| Drug | Concn (μg/ml) in lower layer | Length of growth zone (mm) for an HNCE3 (nonpolar ΔacrA) host containing:
|
||||
|---|---|---|---|---|---|---|
| pSPORTI | pAcrA | pAcrE | pYhiU | pMdtA | ||
| Cholate | 8,000 | 45 | 80 | 80 | 40 | 38 |
| Taurocholate | 6,500 | 35 | 80 | 80 | 40 | 38 |
| Fusidic acid | 35 | 20 | 80 | 45 | 15 | 8 |
| Novobiocin | 30 | 30 | 80 | 59 | 25 | 25 |
| Crystal violet | 12 | 23 | 80 | 80 | 20 | 20 |
| Ethidium bromide | 50 | 21 | 80 | 80 | 18 | 20 |
| Ciprofloxacin | 0.01 | 46 | 80 | 80 | 44 | 45 |
| Chloramphenicol | 12 | 17 | 80 | 32 | 14 | 15 |
| Erythromycin | 30 | 50 | 80 | 80 | 47 | 45 |
| Tetracycline | 6 | 27 | 80 | 35 | 25 | 22 |
a
The length of the plate was 80 mm. Thus, a value of 80 means that the strain grew to the highest concentration found in the plate and that the MIC could have been higher than the concentration in the lower layer. Values shown in boldface represent cells in which the expression of MFP genes produced drug resistance higher than that cells harboring the pSportI vector alone.