Characterization of the antiseptic-resistance gene qacEΔ 1 isolated from clinical and environmental isolates of Vibrio parahaemolyticus and Vibrio cholerae non-O1

The nucleotide sequence and mechanism of action were examined on the antiseptic-resistance gene qacEΔ 1 that had been isolated from Pseudomonas aeruginosa, Vibrio parahaemolyticus and Vibrio cholerae non-O1. The nucleotide sequences of qacEΔ 1 genes isolated from environmental isolates of V. cholerae non-O1 and V. parahaemolyticus differed by one base from that of the gene from P. aeruginosa. Escherichia coli C600 that harbored qacEΔ 1 genes from several strains of Vibrio spp. exhibited low-level resistance to intercalating dyes. The resistance of E. coli cells with these genes to intercalating dyes, such as ethidium bromide, was mediated by an efflux system. Moreover, the activity of QacEΔ1 was inhibited in the presence of calcium channel blockers but not of calmodulin inhibitors. These results indicate that the qacEΔ 1 gene can be function in E. coli and that the gene mediates resistance in a similar manner to the antiseptic-resistance gene smr.