| Abstrakt: |
Resistance Nodulation cell Division (RND) efflux transporters are thought to be involved in mediating multidrug resistance in Gram‐negative bacteria, including Vibrio choleraenon‐O1. There are six operons for putative RND‐type efflux transporters present in the chromosome of V. choleraeO1 including two operons, vexABand vexCD, which had already been identified. All of the six operons were cloned from V. choleraenon‐O1, NCTC4716 by the PCR method, introduced, and expressed in cells of drug hypersusceptible Escherichia coliKAM33 (AacrAB, AydhE). Only vexEFconferred elevated minimum inhibitory concentrations (MICs) of some antimicrobial agents in the E. colicells. However, VexEF did not confer increased MIC of any drug tested in tolC‐deficient E. coliKAM43 cells. On the other hand, when E. coliKAM43 was transformed with vexAB, vexCDor vexEFtogether with tolCVcof V. choleraeNCTC4716, we observed elevated MICs of various antimicrobial agents. Among them, E. coliKAM43 expressing both VexEF and TolCVcshowed much higher MICs and much broader substrate specificity than the other two. We also observed ethidium efflux activity via VexEF‐TolCVc, and the activity required Na+. Thus, VexEF‐TolCVcis either a Na+‐activated or a Na+‐coupled transporter. To our knowledge, this is the first report on the requirement of Na+for an RND‐type efflux transporter. |
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