title: Secondary multidrug efflux pump mutants alter Escherichia coli biofilm growth in the presence of cationic antimicrobial compounds.
abstract: Escherichia coli possesses many secondary active multidrug resistance transporters (MDTs) that confer overlapping substrate resistance to a broad range of antimicrobials via proton and/or sodium motive force. It is uncertain whether redundant MDTs uniquely alter cell survival when cultures grow planktonically or as biofilms. In this study, the planktonic and biofilm growth and antimicrobial resistance of 13 E. coli K-12 single MDT gene deletion strains in minimal and rich media were determined. Antimicrobial tolerance to tetracycline, tobramycin and benzalkonium were also compared for each ΔMDT strain. Four E. coli MDT families were represented in this study: resistance nodulation and cell division members acrA, acrB, acrD, acrE, acrF and tolC; multidrug and toxin extruder mdtK; major facilitator superfamily emrA and emrB; and small multidrug resistance members emrE, sugE, mdtI and mdtJ. Deletions of multipartite efflux system genes acrB, acrE and tolC resulted in significant reductions in both planktonic and biofilm growth phenotypes and enhanced antimicrobial susceptibilities. The loss of remaining MDT genes produced similar or enhanced (acrD, acrE, emrA, emrB, mdtK, emrE and mdtJ) biofilm growth and antimicrobial resistance. ΔMDT strains with enhanced antimicrobial tolerance also enhanced biofilm biomass. These findings suggest that many redundant MDTs regulate biofilm formation and drug tolerance.
authors.affiliation: University of Manitoba, Department of Medical Microbiology and Infectious Diseases, Winnipeg, Manitoba, Canada. Electronic address: Denice.Bay@umanitoba.ca.
authors.forename: Denice C
authors.initials: DC
authors.lastname: Bay
authors.affiliation: Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada.
authors.forename: Carol A
authors.initials: CA
authors.lastname: Stremick
authors.affiliation: University of Manitoba, Department of Medical Microbiology and Infectious Diseases, Winnipeg, Manitoba, Canada.
authors.forename: Carmine J
authors.initials: CJ
authors.lastname: Slipski
authors.affiliation: Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada.
authors.forename: Raymond J
authors.initials: RJ
authors.lastname: Turner
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000494:pharmacology*; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics; D001548:Benzalkonium Compounds / Q000494:pharmacology; D018441:Biofilms / Q000187:drug effects* / Q000254:growth & development; D002412:Cations; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics* / Q000254:growth & development; D017353:Gene Deletion; D026901:Membrane Transport Proteins / Q000235:genetics* / Q000378:metabolism; D008826:Microbial Sensitivity Tests; D009154:Mutation; D010641:Phenotype; D010933:Plankton
chemical_list: D000900:Anti-Bacterial Agents; D001425:Bacterial Outer Membrane Proteins; D001548:Benzalkonium Compounds; D002412:Cations; D026901:Membrane Transport Proteins
keywords: Antibiotic resistance; Antiseptic; Biofilm; Efflux pump; Multidrug resistance (MDR); Planktonic