Characterization of proteobacterial plasmid integron-encoded qac efflux pump sequence diversity and quaternary ammonium compound antiseptic selection in Escherichia coli grown planktonically and as biofilms

Abstract

Qac efflux pumps from proteobacterial multidrug-resistant plasmids are integron encoded and confer resistance to quaternary ammonium compound (QAC) antiseptics; however, many are uncharacterized and misannotated. A survey of.2,000 plasmid-carried qac genes identified 37 unique qac sequences that correspond to one of five representative motifs: QacE, QacED1, QacF/L, QacH/I, and QacG. Antimicrobial susceptibility testing of each cloned qac member in Escherichia coli highlighted distinctive antiseptic susceptibility patterns that were most prominent when cells grew as biofilms.