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

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 >2000 plasmid-encoded qac identified 37 unique qac sequences that correspond to one of five representative motifs: QacE, QacEΔ1, 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.