title: Polyethyleneimine and polyethyleneimine-based nanoparticles: novel bacterial and yeast biofilm inhibitors.
abstract: Biofilms are commonly involved in medical device-related infections. The purpose of this study was to determine the antimicrobial and anti-biofilm activity of polyethyleneimine (PEI) and PEI-based nanoparticles (nanoPEI) against Staphylococcus aureus, Staphylococcus epidermidis, Acinetobacter baumannii and Candida albicans (clinical and ATCC strains), and to evaluate their effect upon biofilm formation on polyurethane (PUR)-like catheters. MICs and minimal lethal concentrations of PEI and nanoPEI were determined according to CLSI microdilution reference protocols. For PEI, the MIC value was 195.31 mg l(-1) for all the bacteria and 48.83 mg l(-1) for the yeast strains. For nanoPEI, the MIC value was 1250 mg l(-1) for all the strains except A. baumannii, for which it was 2500 mg l(-1). Biofilm formation was assessed with PUR-like catheter segments and biofilm metabolic activity was quantified by colorimetry with a tetrazolium reduction assay. Plasma membrane integrity and membrane potential were assessed by flow cytometry after staining microbial cells with a membrane-impermeable dye, propidium iodide, and a membrane-potential marker, DiBAC4(3). PEI inhibited growth of all microbial species; higher concentrations of nanoPEI were needed to inhibit growth of all species. Biofilm formation in the presence of anti-bacterial PEI activity was dose-dependent (except for S. epidermidis) and species-related. NanoPEI at 0.5×MIC and MIC significantly reduced the metabolic activity of biofilms of S. aureus, S. epidermidis and A. baumannii, whereas 2×MIC was required in order to inhibit biofilm metabolic activity.
authors.affiliation: Center for Research in Health Technologies and Information Systems, Faculty of Medicine, University of Porto, Portugal.|School D. Maria II, Rua da Alegria, V.N. Famalicão, Portugal.|Department of Microbiology, Faculty of Medicine, University of Porto, Portugal.
authors.forename: M M
authors.initials: MM
authors.lastname: Azevedo
authors.affiliation: Department of Microbiology, Faculty of Medicine, University of Porto, Portugal.
authors.forename: P
authors.initials: P
authors.lastname: Ramalho
authors.affiliation: Center for Research in Health Technologies and Information Systems, Faculty of Medicine, University of Porto, Portugal.|Department of Microbiology, Faculty of Medicine, University of Porto, Portugal.
authors.forename: A P
authors.initials: AP
authors.lastname: Silva
authors.affiliation: Department of Microbiology, Faculty of Medicine, University of Porto, Portugal.
authors.forename: R
authors.initials: R
authors.lastname: Teixeira-Santos
authors.affiliation: Department of Microbiology, Hospital S. João, Porto, Portugal.|Center for Research in Health Technologies and Information Systems, Faculty of Medicine, University of Porto, Portugal.|Department of Microbiology, Faculty of Medicine, University of Porto, Portugal.
authors.forename: C
authors.initials: C
authors.lastname: Pina-Vaz
authors.affiliation: Burn Unit, Department of Plastic and Reconstructive Surgery, Hospital S. João, Porto.|Center for Research in Health Technologies and Information Systems, Faculty of Medicine, University of Porto, Portugal.|Department of Microbiology, Faculty of Medicine, University of Porto, Portugal.
authors.forename: A G
authors.initials: AG
authors.lastname: Rodrigues
mesh_terms: D040981:Acinetobacter baumannii / Q000187:drug effects* / Q000254:growth & development / Q000502:physiology; D000890:Anti-Infective Agents / Q000494:pharmacology*; D018441:Biofilms / Q000187:drug effects* / Q000254:growth & development; D002176:Candida albicans / Q000187:drug effects* / Q000254:growth & development / Q000502:physiology; D057785:Catheters / Q000382:microbiology; D002462:Cell Membrane / Q000187:drug effects; D004734:Energy Metabolism / Q000187:drug effects; D008564:Membrane Potentials / Q000187:drug effects; D008826:Microbial Sensitivity Tests; D050296:Microbial Viability / Q000187:drug effects; D053758:Nanoparticles; D011094:Polyethyleneimine / Q000494:pharmacology*; D011140:Polyurethanes; D013210:Staphylococcus / Q000187:drug effects* / Q000254:growth & development / Q000502:physiology
chemical_list: D000890:Anti-Infective Agents; D011140:Polyurethanes; D011094:Polyethyleneimine