title: In vitro activity of gentamicin, vancomycin or amikacin combined with EDTA or l-arginine as lock therapy against a wide spectrum of biofilm-forming clinical strains isolated from catheter-related infections.
abstract: OBJECTIVE
  Treatment of catheter-related bloodstream infections (CRBSI) is hampered by the characteristic tolerance of bacterial biofilms towards antibiotics. Our objective was to study the effect of the combination of antibiotics and the alkaline amino acid l-arginine or the cation chelator EDTA on the bacterial killing of in vitro biofilms formed by an array of clinical strains responsible for CRBSI and representative of epidemiologically relevant bacterial species.
  
  
  METHODS
  Among 32 strains described in a previous clinical study, we focused on the most antibiotic-tolerant strains including CoNS (n = 4), Staphylococcus aureus (n = 4), Enterococcus faecalis (n = 2), Pseudomonas aeruginosa (n = 4) and Enterobacteriaceae (n = 4). We used an in vitro biofilm model (96-well plate assay) to study biofilm tolerance and tested various combinations of antibiotics and non-antibiotic adjuvants. Gentamicin, amikacin or vancomycin was combined with disodium EDTA or l-arginine for 24 h to reproduce the antibiotic lock therapy (ALT) approach. Killing of biofilm bacteria was measured by cfu quantification after a vigorous step of pipetting up and down in order to detach all biofilm bacteria from the surface of the wells.
  
  
  RESULTS
  Both of our adjuvant strategies significantly increased the effect of antibiotics against biofilms formed by Gram-positive and Gram-negative bacterial pathogens. The combination of gentamicin + EDTA was active against all tested strains apart from one P. aeruginosa. The combination of gentamicin + l-arginine was active against most of the tested strains with the notable exception of CoNS for which no potentiation was observed. We also demonstrated that amikacin + EDTA was active against Gram-negative bacteria and that vancomycin + EDTA was active against Gram-positive bacteria.
  
  
  CONCLUSIONS
  The addition of EDTA enhanced the activity of gentamicin, amikacin and vancomycin against biofilms formed by a wide spectrum of bacterial strains responsible for CRBSI.
authors.affiliation: Institut Pasteur, Genetics of Biofilms Unit, Department of Microbiology, 28 rue du Dr Roux, 75724 Paris cedex 15, France Sorbonne Paris Cité, AP-HP, Hôpital Necker Enfants Malades, Centre d'Infectiologie Necker-Pasteur and Institut Imagine, Université Paris Descartes, 149 Rue de Sèvres, 75743 Paris cedex 15, France david.lebeaux@yahoo.fr.
authors.forename: David
authors.initials: D
authors.lastname: Lebeaux
authors.affiliation: Service de Microbiologie, Hôpital Beaujon, AP-HP, Clichy, France.
authors.forename: Véronique
authors.initials: V
authors.lastname: Leflon-Guibout
authors.affiliation: Institut Pasteur, Genetics of Biofilms Unit, Department of Microbiology, 28 rue du Dr Roux, 75724 Paris cedex 15, France.
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Ghigo
authors.affiliation: Institut Pasteur, Genetics of Biofilms Unit, Department of Microbiology, 28 rue du Dr Roux, 75724 Paris cedex 15, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Beloin
mesh_terms: D000583:Amikacin / Q000494:pharmacology; D000890:Anti-Infective Agents / Q000494:pharmacology*; D001120:Arginine / Q000494:pharmacology*; D001419:Bacteria / Q000187:drug effects* / Q000302:isolation & purification; D018441:Biofilms / Q000187:drug effects*; D055499:Catheter-Related Infections / Q000382:microbiology; D002614:Chelating Agents / Q000494:pharmacology*; D015169:Colony Count, Microbial; D004203:Disinfection / Q000379:methods; D004492:Edetic Acid / Q000494:pharmacology; D005839:Gentamicins / Q000494:pharmacology; D006801:Humans; D050296:Microbial Viability / Q000187:drug effects; D014640:Vancomycin / Q000494:pharmacology
chemical_list: D000890:Anti-Infective Agents; D002614:Chelating Agents; D005839:Gentamicins; D014640:Vancomycin; D000583:Amikacin; D001120:Arginine; D004492:Edetic Acid
keywords: adjuvant strategy; aminoglycosides; antibiotic lock therapy; in vitro models; persisters