title: Extracellular DNA impedes the transport of vancomycin in Staphylococcus epidermidis biofilms preexposed to subinhibitory concentrations of vancomycin.
abstract: Staphylococcus epidermidis biofilm formation is responsible for the persistence of orthopedic implant infections. Previous studies have shown that exposure of S. epidermidis biofilms to sub-MICs of antibiotics induced an increased level of biofilm persistence. BODIPY FL-vancomycin (a fluorescent vancomycin conjugate) and confocal microscopy were used to show that the penetration of vancomycin through sub-MIC-vancomycin-treated S. epidermidis biofilms was impeded compared to that of control, untreated biofilms. Further experiments showed an increase in the extracellular DNA (eDNA) concentration in biofilms preexposed to sub-MIC vancomycin, suggesting a potential role for eDNA in the hindrance of vancomycin activity. Exogenously added, S. epidermidis DNA increased the planktonic vancomycin MIC and protected biofilm cells from lethal vancomycin concentrations. Finally, isothermal titration calorimetry (ITC) revealed that the binding constant of DNA and vancomycin was 100-fold higher than the previously reported binding constant of vancomycin and its intended cellular d-Ala-d-Ala peptide target. This study provides an explanation of the eDNA-based mechanism of antibiotic tolerance in sub-MIC-vancomycin-treated S. epidermidis biofilms, which might be an important factor for the persistence of biofilm infections.
authors.affiliation: Faculty of Engineering and the Environment, University of Southampton, Southampton, United Kingdom nd2m09@gmail.com.
authors.forename: Natalya
authors.initials: N
authors.lastname: Doroshenko
authors.affiliation: Department of Microbiology, University of Washington, Seattle, Washington, USA.
authors.forename: Boo Shan
authors.initials: BS
authors.lastname: Tseng
authors.affiliation: National Institute for Health Research Southampton Respiratory Biomedical Research Unit, Southampton Centre for Biomedical Research, University Hospital Southampton NHS Foundation Trust, Southampton, United Kingdom Centre for Biological Sciences, Faculty of Natural and Environmental Sciences and Institute for Life Sciences, University of Southampton, Southampton, United Kingdom.
authors.forename: Robert P
authors.initials: RP
authors.lastname: Howlin
authors.affiliation: Centre for Infection and Immunity, School of Medicine, Dentistry and Biomedical Sciences, Queen's University of Belfast, Belfast, United Kingdom.
authors.forename: Jill
authors.initials: J
authors.lastname: Deacon
authors.affiliation: Faculty of Engineering and the Environment, University of Southampton, Southampton, United Kingdom.
authors.forename: Julian A
authors.initials: JA
authors.lastname: Wharton
authors.affiliation: Faculty of Engineering and the Environment, University of Southampton, Southampton, United Kingdom.
authors.forename: Philipp J
authors.initials: PJ
authors.lastname: Thurner
authors.affiliation: School of Pharmacy, Queen's University of Belfast, Belfast, United Kingdom.
authors.forename: Brendan F
authors.initials: BF
authors.lastname: Gilmore
authors.affiliation: Department of Microbiology, University of Washington, Seattle, Washington, USA.
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Parsek
authors.affiliation: Faculty of Engineering and the Environment, University of Southampton, Southampton, United Kingdom Centre for Microbial Interface Biology, Departments of Microbial Infection and Immunity and Orthopedics, The Ohio State University, Columbus, Ohio, USA.
authors.forename: Paul
authors.initials: P
authors.lastname: Stoodley
mesh_terms: D000900:Anti-Bacterial Agents / Q000378:metabolism / Q000494:pharmacology*; D018441:Biofilms / Q000187:drug effects* / Q000254:growth & development; D001692:Biological Transport / Q000187:drug effects; D001896:Boron Compounds / Q000737:chemistry; D004269:DNA, Bacterial / Q000378:metabolism / Q000494:pharmacology*; D005456:Fluorescent Dyes / Q000737:chemistry; D008826:Microbial Sensitivity Tests; D018613:Microscopy, Confocal; D012995:Solubility; D013194:Staining and Labeling; D013212:Staphylococcus epidermidis / Q000187:drug effects* / Q000502:physiology; D014640:Vancomycin / Q000037:antagonists & inhibitors* / Q000378:metabolism / Q000494:pharmacology
chemical_list: C095489:4,4-difluoro-4-bora-3a,4a-diaza-s-indacene; D000900:Anti-Bacterial Agents; D001896:Boron Compounds; D004269:DNA, Bacterial; D005456:Fluorescent Dyes; D014640:Vancomycin